ELEMENTAL CHEMISTRY

Ultramarine Blue

2023-06-23T17:19:00.001+05:30

ULTRAMARINE BLUE

Synthetic ultramarine blue is the most widely used blue pigment in the present time. Ultramarine blue pigment is insoluble in water and dark blue in colour. In 1928, blue ultramarine was first prepared by Guiment and Gamelin. The ultramarine blue pigment is a complex silicate of aluminium and sodium assisted with about 12% sulphur.

Blue, green and white are three varieties of ultramarine. Among these three varieties, blue colour variety is the most popular and this blue ultramarine is used as a pigment. This blue colour variety can be prepared from green or white ultramarine. These ultramarine pigments are affected by acid but stable in alkali and light. Due to liberation of H₂S gas, these pigments are affected by acid. The composition of three types of ultramarine are as follows---

Blue ----- Na₅Al₃Si₂S₃O₁₂

Green ----- Na₅Al₃Si₂S₂O₁₂

White ----- Na₅Al₃Si₃SO₁₂

The ultramarine composition is however not stoichiometric. Because the degree of exchange that takes place depends upon the various factors. These factors are solution concentration, heating time etc.

Preparation of Blue Ultramarine

When a mixture of sodium carbonate (soda ash), kaolin, charcoal, quartz, sulfur and resin is heated blue ultramarine is prepared. [It is very important that iron should not present in the raw materials. If iron present in the raw materials it appreciably dulls the colour and forms a white mass. In presence of air this white mass changes to green.] After heating, the product is cooled and powdered. If sodium carbonate (soda ash) in the raw materials is substituted by sodium sulphate, then darker blue colour is produced.

For the manufactured of ultramarine there are three methods--

(1) Sulphate process--- In the sulphate process kaolin, sodium sulphate and charcoal are heated together.

(2) Soda sulphate process--- In the soda sulphate process kaolin, sodium carbonate (soda ash), sodium sulphate, sulfur and tar are heated together.

(3) Soda process--- In the soda process kaolin, sodium carbonate (soda ash), sulfur, colophonium and tar heated together.

The depth of the colour of the ultramarine increases with the increase in the amount of sulfur content. In the ultramarine, sulfur present is in the same form as in the polysulphides, is the probable reason for the colour of ultramarine. In the blue ultramarine Na⁺ ion is present. When Na⁺ ion is replaced by other cations such as K⁺ ion or Ag⁺ ion, it is found that the colour of ultramarine changes to various colour, depending on the cations. This indicates that within the alumino silicate skeleton, the cation present, have a potential influence on the colour.

Uses of Ultramarine

(1) Ultramarine blue is widely used for wall painting.

(2) It is used for laundry purpose. It is used for neutralize the yellowish tone in cotton or linen fabrics.

(3) For painting woods ultramarine blue used as a pigment.

(4) For whitening, paper and other products, ultramarine is also used.

Limitation

Ultramarine can not be used as a cooling material or iron articles because in ultramarine large percent of sulfur present. Due to possibility for the formation of PbS, it can not be mixed with lead pigments.

Electron Affinity

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ELECTRON AFFINITY

Electron affinity (EA) of an atom is defined as the energy released when an electron is added to the valance shell of a gaseous atom in its ground state.

In other words, electron affinity of an atom is defined as the energy released when a gaseous atom captures an electron.

X(g) + electron → X^-(g) + EA

The process of addition of an electron to an atom is an exothermic process. Electron affinity is also called enthalpy of electron attachment because electron affinity is the energy involved in addition of an electron to an atom. According to our usual thermodynamic convention, since electron affinity is the energy released it should be represented with a negative sign, but unfortunately electron affinity values are normally represented with a positive sign.

However, negative electron affinity values are also known. Such value indicates that the species does not want to have an extra electron. Subsequent addition of electrons to an atom gives successive electron affinity values such as (EA)₁, (EA)₂, (EA)₃ --- etc. Once an electron is added to an atom, subsequent entry of 2 nd, 3 rd--- etc, electron would involve repulsion between the existing electrons and the entering electrons. In such cases energy would be required to push the electron against the interelectronic repulsion. Hence the 2 nd, 3 rd etc electron affinity values are always negative.

Electron affinity values are expressed in ev/atom, Kcal/mole and KJ/mole.

Electron affinity values can not obtain experimentally. Electron affinity values are obtained indirectly from Born-Haber Cycle.

Periodic Trend of Electron Affinity

(1) Variation Along a Period

On moving from left to right along a period that is from alkali metals to halogens along a period, the radius of atom decreases and nuclear charge increases. As a result of these two factors, the attractive force between the nucleus and the added electrons is increase. Therefore, the atom has greater tendency to captures an electron. So, generally electron affinity values gradually increase from left to right along a period, that is from alkali metals to halogens. Since, each period start with an alkali metal, it lies extreme left in periodic table and it has the lowest value of electron affinity. Halogen lie extreme right in the periodic table, it has the highest value of electron affinity.

(2) Variation Along a Group

On moving from top to bottom along a group that is downwards along a group, the radius of atom increases and the nuclear charge also increases on the same direction. The increase in atomic radius decreases the electron affinity values and increase nuclear charge increases the electron affinity values. Here the effect of atomic radius overcome the effect of nuclear charge. So, the value of electron affinity decreases on going from top to bottom along a group that is downwards along a group.

Factors Affecting the Magnitude of Electron Affinity

(1) Size of the Atom

The smaller is the size of the atom, the greater is the electron affinity value.

Electron Affinity ∝ Atomic Size

For smaller atom the attraction of the nucleus for the added electron is stronger. So, the electron affinity value is greater for smaller atom.

(2) Nuclear Charge

Electron affinity directly proportional to the nuclear charge.

Electron Affinity ∝ Nuclear Charge

With increase in nuclear charge the attraction of the nucleus for the added electron increases. Therefore, the electron affinity value increases with increase in nuclear charge.

(3) Electron Configuration

Atoms with stable electronic configuration, that is with half filled or full filled electronic configuration have little or no tendency to accept any more electron. So, they have low or negative electron affinity values. Tendency to attain stable electronic configuration is reflected by high electron affinity value.

Electron Affinity of Some Cases

(1) The electron affinity values of the noble gases are negative---

The valance shell electronic configurations of noble gases are ns² np⁶ (He has 1s² configuration). So, noble gas atoms have stable electronic configuration. They have no tendency to captures any extra electron. Therefore, electron affinity values of noble gases are negative. That is energy will be required to push the electron in the valance shell of noble gases.

(2) Halogens possess large positive electron affinity values---

The valance shell electron configuration of halogens is ns² np⁵. So, the halogens atoms have one electron short to fulfill their octet and to obtained stable noble gas electronic configuration. So, to attain stable electronic configuration they have very high tendency to captures an electron. Accordingly, halogens possess large positive electron affinity values.

(3) Electron affinity values of Beryllium (Be) Magnesium (Mg) and Nitrogen (N) are negative---

Valance shell electron configurations of Beryllium (Be) and magnesium (Mg) are ns², so they have filled s shell. Valance shell electron configuration of nitrogen (N) is ns² np³, so nitrogen has half filled p shell. According to Hund’s rule a half filled shell or full filled shell attains extra stability. Hence, the atoms such as Be, Mg and N would be much reluctant to captures extra electron. So, the electron affinity values of Be, Mg and N are negative.

(4) The 2 nd electron affinity value of oxygen (O) and sulfur (S) are negative---

When an atom captures an electron an uninegative ion is formed.

O(g) + e^- → O^-(g) + Energy

S(g) + e^- → S^-(g) + Energy

So, the 1 st electron affinity value is positive for oxygen and sulfur, because they have captured an electron readily. In spite of their high tendency to attain stable electronic configuration, entry of the second electron will be difficult. Because entry of the second electron would involve repulsion between the existing electrons and the entering electron. In such situation energy will be required to push the electron against such repulsion. So, the second electron affinity value of oxygen and sulfur are negative.

Magnesium

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MAGNESIUM

Symbol --- Mg

Abundance --- 2% in the earth’s crust.

Physical state (STP)--- solid

Elemental category --- alkaline earth metal

Colour --- shiny grey

Discovery --- Joseph Black

Atomic no --- 12

Atomic weight --- 24.305

Period --- 3

Group --- 2 or IIA

Block --- s block

Known isotopes --- ₁₂Mg¹⁹, ₁₂Mg²⁰, ₁₂Mg²¹, ₁₂Mg²², ₁₂Mg²³, ₁₂Mg²⁴, ₁₂Mg²⁵, ₁₂Mg²⁶, ₁₂Mg²⁷, ₁₂Mg²⁸, ₁₂Mg²⁹, ₁₂Mg³⁰, ₁₂Mg³¹, ₁₂Mg³², ₁₂Mg³³, ₁₂Mg³⁴, ₁₂Mg³⁵, ₁₂Mg³⁶, ₁₂Mg³⁷, ₁₂Mg³⁸

Main isotopes --- ₁₂Mg²⁴, ₁₂Mg²⁵, ₁₂Mg²⁶

Isotopic abundance --- ₁₂Mg²⁴(78.99%), ₁₂Mg²⁵(10.005%), ₁₂Mg²⁶(11.005%)

Melting Point --- 650 ⁰C (923.15 K)

Boiling Point --- 1090 ⁰C (1363.15 K)

Heat of Fusion --- 8.47 KJ/mol

Heat of Vaporisation --- 127.5 KJ/mol

Molar heat capacity --- 24.855 J/(mol-K)

Density --- 1.7 g/cm³

Molar volume --- 0.000013

Electron configuration --- [Ne] 3s²

Electrons per shell --- 2 (1 st shell), 8 (2 nd shell), 2 (3 rd shell)

Oxidation state --- +2

Valance --- 2

Electronegativity --- 1.31 (Pauling scale)

Ionisation energy --- 737 KJ/mol (1 st), 1450 KJ/mol (2 nd), 7731 KJ/mol (3 rd), 10542 KJ/mol (4 th)

Covalent radius --- 141 pm

Atomic radius --- 160 pm

Van der Waals radius --- 173 pm

Radius of Mg²⁺ (6-coordinated) --- 72 pm

E⁰(V) for [Mg²⁺(aq)/Mg(s)] --- – 2.37

Natural occurrence --- primordial

Crystal structure --- hexagonal close packed (hcp)

Specific heat --- 1020 J/(Kg K) (solid phase)

Thermal expansion --- 24.9 μm/(m-K) (at 298 K)

Thermal conductivity --- 156 W/(m-K)

Electrical resistivity --- 43.8 nΩ-m (at 293K)

Speed of sound --- 4939 m/s (at 298 K)

Magnetic type --- paramagnetic

Mass magnetic susceptibility --- 6.88 x 10^-9 m³/Kg

Molar magnetic susceptibility --- 1.69 x 10^-10 m³/mol

Volume magnetic susceptibility --- 1.2 x 10^-5

Mohs hardness --- 2.5

Brinell hardness --- 260 MPa

Poisson ratio --- 0.29

Young’s modulus --- 45 Gpa

Shear modulus --- 17 GPa

Bulk modulus --- 35.5 GPa

Lattice angles --- π/2, π/2, 2π/3

Lattice constants --- 320.88 pm, 320.88 pm, 521.09 pm

Quantum numbers --- ¹S₀

Neutron cross section --- 6.3 x 10^-2

Neutron mass absorption --- 1 x 10^-4

Oils Fats and Waxes

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OILS FATS AND WAXES

Oils--- Oils are esters of higher fatty acids. Oils contain a large proportion of glycerides of unsaturated acid. Melting point of oil is below 20⁰C.

Fats--- Fats are esters of higher fatty acids. Fats contain a large proportion of glycerides of saturated acid. Melting point of fat is above 20⁰C.

Classification of Oils and Fats

(1) Depending on uses oils and fats are two types---

(i) Edible--- Those oils and fats are uses for cooking purpose or eating purpose are known as edible oils or fats.

(ii) Inedible--- Those oils and fats are uses for making soaps, detergents, paintings etc are known as inedible oils or fats.

(2) Depending on nature of the carbon chain, oils and fats are three types---

(i) Non-drying oils or fats--- If the carbon chain present in oil or fat is saturated, then that oil or fat is called non-drying oil or fat.

(ii) Semi-drying oils or fats--- If the carbon chain present in oil or fat have some degree of unsaturation, then that oil or fat is called semi-drying oil or fat.

(iii) Drying oils or fats--- If the carbon chain present in oil or fat is unsaturated, then that oil or fat is called drying oil or fat.

(3) Depending on the source of availabilities oils and fats are three types---

(i) Vegetable oils or fats--- Oils or fats extracted from vegetable source are known as vegetable oils or fats.

(ii) Animal oils or fats--- Oils or fats extracted from animal source are known as animal oils or fats.

(iii) Mineral oils or fats--- Oils or fats extracted from mineral source are known as mineral oils or fats.

Waxes--- Waxes are esters of monohydric alcohols with higher fatty acid. The molecular weight of these alcohols is very large. Waxes are non-crystalline esters.

Depending on the source of availabilities waxes are five types, such as----

(i) Animal waxes

(ii) Vegetable waxes

(iii) Mineral waxes

(iv) Mineralised vegetable waxes

(v) Synthetic waxes

Difference Between Fats and Oils

If we consider the Chemical properties there is no difference between fats and oils, both fats and oils consist of mixed glycerides. The difference between fats and oils is merely physical one of consistency.

(i) Melting point of fat is above 20⁰C, whereas melting point of oil is below 20⁰C. Coconut oil and ghee are fats in winter but oils in summer.

(ii) A large proportion of glycerides of saturated fatty acids are present in fats, whereas a large proportion of glycerides of unsaturated fatty acids are present in oils.

(iii) The iodine value of oils is high due to presence of higher unsaturation in oils, whereas the iodine value of fats is low.

(iv) Due to presence of unsaturation that is double bond in oils, oils can be hydrogenated by using H₂ and Ni catalyst. Since fats contain a large proportion of glycerides of saturated fatty acid, so fats can not be hydrogenated. By heating fats can be converted to oils.

Difference Between Vegetable and Mineral Oils

(i) The vegetable oils have high flash point, and this might be 326⁰C. Whereas flash point is 200⁰C for most mineral oils.

(ii) Mineral oils have zero acid value but vegetable oils have definite acid value.

(iii) Vegetable oils contain a large proportion of glycerides of saturated and unsaturated fatty acids, so they can not be distilled with the steam, and vegetable oils are called fine oils. Mineral oils are mixture of various hydrocarbon such as kerosene, paraffin, petroleum etc. Mineral oils are highly volatile, possess unpleasant smell and can be distilled with steam.

Examples of Animal Oils

(i) Cord-liver oil

(ii) Shark liver oil

(iii) Fish oil

(iv) Whale oil

Examples of Vegetable Oils

(i) Mustard oil

(ii) Coconut oil

(iii) Seed oil

(iv) Linseed oil

(v) Castor oil

Examples of Mineral Oils

(i) Kerosene oil

(ii) Diesel

(iii) Petroleum oil

(iv) Paraffin oil

Sodium

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SODIUM

Symbol --- Na

Abundance --- 28300 ppm (total abundance), 22700 ppm in the earth’s crust. Sodium is fifth most abundant metal (after Al, Fe, Ca and Mg).

Physical state (STP)--- solid

Elemental category --- alkali metal

Colour --- silvery white metallic

Discovery --- Humphry Davy

Atomic no --- 11

Atomic weight --- 22.989

Period --- 3

Group --- 1 or IA

Block --- s block

Known isotopes --- ₁₁Na¹⁸, ₁₁Na¹⁹, ₁₁Na²⁰, ₁₁Na²¹, ₁₁Na²², ₁₁Na²³, ₁₁Na²⁴, ₁₁Na²⁵, ₁₁Na²⁶, ₁₁Na²⁷, ₁₁Na²⁸, ₁₁Na²⁹, ₁₁Na³⁰, ₁₁Na³¹, ₁₁Na³², ₁₁Na³³, ₁₁Na³⁴, ₁₁Na³⁵

Main isotope --- ₁₁Na²³

Isotopic abundance --- ₁₁Na²³ (100%)

Melting Point --- 97.8 ⁰C (370.95 K)

Boiling Point --- 883 ⁰C (1156.15 K)

Critical Temperature --- 2573 K

Critical Pressure --- 35 MPa

Heat of Fusion --- 2.6 KJ/mol

Heat of Vaporisation --- 97.3 KJ/mol

Molar heat capacity --- 28.25 J/(mol-K)

Density --- 0.97 g/cm³

Molar volume --- 0.000023

Electron configuration --- [Ne] 3s¹

Electrons per shell --- 2 (1 st shell), 8 (2 nd shell), 1 (3 rd shell)

Oxidation state --- +1

Valance --- 1

Electronegativity --- 0.93 (Pauling scale)

Electron affinity --- 52.5 KJ/mol

Ionisation energy --- 495.7 KJ/mol (1 st), 4563 KJ/mol (2 nd), 6910 KJ/mol (3 rd), 9542 KJ/mol (4 th)

Covalent radius --- 166 pm

Atomic radius --- 186 pm

Van der Waals radius --- 227 pm

Ionic radius (octahedral) --- 102 pm

Hydrated radii --- 276 pm

E⁰ for [Na⁺(aq) + e = Na(s)] --- – 2.71

Natural occurrence --- primordial

Crystal structure --- body centered cubic (bcc)

Specific heat --- 1230 J/(Kg K) (solid phase)

Thermal expansion --- 71 μm/(m-K)

Thermal conductivity --- 142 W/(m-K)

Electrical resistivity --- 47.5 nΩ-m

Speed of sound --- 3200 m/s (at 20 ⁰C)

Magnetic type --- paramagnetic

Mass magnetic susceptibility --- 8.79 x 10^-9 m³/Kg

Molar magnetic susceptibility --- 1.9 x 10^-10 m³/mol

Volume magnetic susceptibility --- 8.5 x 10^-6

Mohs hardness --- 0.5

Brinell hardness --- 0.68 MPa

Young’s modulus --- 10 Gpa

Shear modulus --- 3.3 GPa

Bulk modulus --- 6.3 GPa

Lattice angles --- π/2, π/2, π/2

Lattice constants --- 428.9 pm, 428.9 pm, 428.9 pm

Quantum numbers --- ²S_1/2

Neutron cross section --- 5.3 x 10^-1

Neutron mass absorption --- 7 x 10^-4

Preparation of Alkanes

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PREPARATION OF ALKANES

Alkanes can be prepared by various ways. General methods of preparation of alkanes are--

(1) From Unsaturated Hydrocarbons

Alkanes are prepared by the catalytic reduction of unsaturated hydrocarbons such as alkene or alkyne in the presence of a suitable catalyst such as Ni, Pt, Pd, Raney Ni etc. Here hydrogen is added to an unsaturated hydrocarbon (alkene or alkyne) in the presence of a catalyst. This process is known as hydrogenation.

The catalytic hydrogenation reaction takes place at normal temperature and pressure if we use Raney Ni, Pt or Pd as a catalyst.

But if we use Ni as a catalyst, then the catalytic hydrogenation reaction takes place at 200 ⁰C – 300 ⁰C. The catalytic hydrogenation reaction in presence of a Ni catalyst at 200 ⁰C – 300 ⁰C is known as Sabatier-Senderens reduction.

(2) From Alkyl Halides

Alkanes can be prepared from alkyl halides in different ways---

(A) Through Grignard Reagent

When alkyl halide heated with magnesium powder in ether solution, alkyl magnesium halide (R―Mg―X) is produced. This alkyl magnesium halide (R―Mg―X) is known as Grignard reagent.

R―X + Mg → R―Mg―X

C₂H₅―I + Mg → C₂H₅―Mg―I

When Grignard reagent treated with water or dilute acid, alkane is produced.

R―Mg―X + H₂O → RH + Mg(OH)X

C₂H₅―Mg―I + H₂O → C₂H₆ + Mg(OH)I

(B) By Wurtz Reaction

In dry ether solution at normal temperature the reaction of two molecules of alkyl halide (preferably the bromide or iodide) with two molecules of pure and dry metallic sodium produce alkane.

R₁―X + 2Na + R₂―X → R₁―R₂ + 2NaX

CH₃―Br + 2Na + CH₃―Br → CH₃―CH₃

+ 2NaBr

If we use two types of alkyl halide, then mixture of alkanes is produced. It is difficult to separate this mixture of alkanes, because their close boiling point.

CH₃―Br + 2Na + C₂H₅―Br → CH₃―CH₃ + C₂H₅―C₂H₅ + CH₃―C₂H₅ + 2NaBr

This Wurth reaction is very useful for the synthesis of symmetrical alkane.

(C) By Corey-House Synthesis

In dry ether solution at normal temperature the reaction of alkyl halide with pure and dry metallic lithium produced alkyl lithium.

RX + 2Li → RLi + LIX

C₂H₅I + 2Li → C₂H₅Li + LiI

Reaction of alkyl lithium (RLi) with cuprous iodide (CuI) produced lithium dialkyl cuprate (R₂CuLi).

2RLi + CuI → R₂CuLi + LiI

2C₂H₅Li + CuI → (C₂H₅)₂CuLi + LiI

Reaction of lithium dialkyl cuprate (R₂CuLi) with another molecule of alkyl halide produced alkane.

R₂CuLi + R'X → R―R' + RCu +LiX

(C₂H₅)₂CuLi + CH₃I → C₂H₅―CH₃ + C₂H₅Cu + LiI

R and R' may be same or different. R group may be primary, secondary or tertiary but R' group always primary.

This Corey-House reaction is very useful for the formation of both symmetrical and unsymmetrical alkane.

(D) Reduction of Alkyl Halides

(i) Alkane is prepared by the reduction of alkyl halide by Zn and HCl.

C₂H₅Cl + Zn + HCl → C₂H₆ + ZnCl₂

(ii) Alkane is prepared by the reduction of alkyl halide by Zn and NaOH.

Zn + 2NaOH → Na₂ZnO₂ + 2[H]

R―X + 2[H] → R―H + HX

(iii) When alkyl halide is reduced by Zn-Cu couple in presence of alcohol alkane is produced.

Zn → Zn²⁺ + 2e

R―X + e → R∙ + X^-

R∙ + e → R:^-

R:^- + C₂H₅OH → R―H + C₂H₅O^-

(iv) When alkyl halide is reduced by LiAlH₄, NaBH₄ or Ph₃SnH alkane is produced.

R―X + H^- → R―H + X^-

(v) When alkyl halide is reduced by H₂ in presence of Pd-C or Raney Ni, alkane is produced.

R―X + H₂ → R―H + HX

(vi) When alkyl iodide is reduced by hydroiodic acid (HI) and red phosphorus at 150 ⁰C, alkane is produced.

C₂H₅―I + HI → C₂H₆ + I₂

(3) From Carbonyl Compounds

Alkane can be prepared from carbonyl compounds such as aldehyde and ketone by Clemensen reduction process and Wolf-Kishner reduction process.

(A) By Clemmensen Reduction

When carbonyl compounds such as aldehydes and ketones are heated with zinc amalgam (Zn/Hg) and concentrated HCl, carbonyl compounds reduced to form alkane.

(B) By Wolff-Kishner Reduction

Carbonyl compounds such as aldehydes and ketones react with hydrazine (H₂N―NH₂) to formed hydrazone. When the resulting hydrazone is heated with sodium ethoxide (NaOC₂H₅) and ethylene glycol (HOH₂C―CH₂OH) at 180 ⁰C, alkane is produced.

(4) From Carboxylic Acid

Alkane can be prepared from carboxylic acid by two methods. One is decarboxylation process and another is Kolbe’s electrolytic method.

(A) By Decarboxylation Process

Alkane is produced when carboxylic acid is heated with soda lime (NaOH + CaO). In this reaction CO₂ is removed, so it is called decarboxylation reaction.

This is a degradation reaction, because in this process the number of carbon atom in the produced alkane is one less than that of the carboxylic acid.

(B) Kolbe’s Electrolytic Method

Electrolysis of a concentrated and cool aqueous solution of sodium or potassium salts of monocarboxylic acid using platinum electrodes produced alkane at the anode.

2R―COOK + 2H₂O → [R―R + 2CO₂(anode)] + [H₂ + 2KOH (cathode)]

2CH₃COOK + 2H₂O → [C₂H₆ + 2CO₂(anode)] + [H₂ + 2KOH (cathode)]

Kolbe’s method of electrolysis is suitable for the preparation of even number of carbon atom alkane, but not suitable for the preparation of odd number of carbon atom alkane.

(5) From Alkyl Borane

Reaction of alkene with borane produced trialkyl borane.

3R―CH=CH₂ + B₂H₆ → (R―CH₂―CH₂)₃B

Alkane is produced by hydrolysis of the resulting trialkyl borane with acid.

(RCH₂CH₂)₃B + 3CH₃COOH → 3RCH₂CH₃+ (CH₃COO)₃B

(6) From Alcohol

When alcohol is reduced by red phosphorus (P) and hydroiodic acid (HI) in a closed vessel at 150 ⁰C, alkane is produced.

Neon

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NEON

Symbol --- Ne

Abundance --- 18 ppm by volume in dry air and 7x10^-5 ppm by weight in the earth’s crust

Physical state (STP)--- gas

Elemental category --- noble gas

Gas phase --- monoatomic

Colour --- colourless

Discovery --- William Ramsay

Atomic no --- 10

Atomic weight --- 20.179

Period --- 2

Group --- 18 or VIIIA

Block --- p block

Known isotopes --- ₁₀Ne¹⁶, ₁₀Ne¹⁷, ₁₀Ne¹⁸, ₁₀Ne¹⁹, ₁₀Ne²⁰, ₁₀Ne²¹, ₁₀Ne²², ₁₀Ne²³, ₁₀Ne²⁴, ₁₀Ne²⁵, ₁₀Ne²⁶, ₁₀Ne²⁷, ₁₀Ne²⁸, ₁₀Ne²⁹, ₁₀Ne³⁰, ₁₀Ne³¹, ₁₀Ne³², ₁₀Ne³³

Main isotopes --- ₁₀Ne²⁰, ₁₀Ne²¹, ₁₀Ne²²

Isotopic abundance --- ₁₀Ne²⁰ (90.38%), ₁₀Ne²¹ (0.30%), ₁₀Ne²² (9.32%)

Melting Point --- – 248.6 ⁰C (24.55 K)

Boiling Point --- – 246.05 ⁰C (27.1 K)

Triple Point --- 24.55 K, 43.35 kPa

Critical Temperature --- 44.5 K

Critical Pressure --- 2.76 MPa

Heat of Fusion --- 0.336 KJ/mol

Heat of Vaporisation --- 1.8 KJ/mol

Molar heat capacity --- 20.8 J/(mol-K)

Density --- 0.9 g/L (at STP)

Molar volume --- 0.0224

Solubility (water) --- 10.5 cm³/L (at 20 ⁰C)

Electron configuration --- [He] 2s² 2p⁶

Electrons per shell --- 2 (1 st shell), 8 (2 nd shell)

Oxidation state --- 0

Valance --- 0

Electron affinity --- 0 KJ/mol

Ionisation energy --- 2080 KJ/mol (1 st), 3951.5 KJ/mol (2 nd), 6122.3 KJ/mol (3 rd), 9372 KJ/mol (4 th)

Covalent radius --- 58 pm

Van der Waals radius --- 154 pm

Natural occurrence --- primordial

Crystal structure --- face centered cubic (fcc)

Specific heat --- 1030 J/(Kg K) (gas)

Speed of sound --- 435 m/s (gas, at 0⁰C)

Thermal conductivity --- 0.049 W/(m K)

Magnetic type --- diamagnetic

Mass magnetic susceptibility --- – 4.0 x 10^-9 m³/Kg

Molar magnetic susceptibility --- – 8.25 x 10^-11 m³/mol

Volume magnetic susceptibility --- – 3.7 x 10^-9

Bulk modulus --- 654 GPa

Lattice angles --- π/2, π/2, π/2

Lattice constants --- 442.7 pm, 442.7 pm, 442.7 pm

Quantum numbers --- ¹S₀

Neutron cross section --- 4 x 10^-2

Neutron mass absorption --- 5.9 x 10^-4

Refractive index --- 1.00006

Electronegativity

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ELECTRONEGATIVITY

Electronegativity (EN) of an atom in a molecule is defined as its tendency to attract the bonding electrons in a chemical bond towards itself.

In a heteronuclear chemical bond X―Y between two different atoms X and Y, [where the electronegativity of X and Y are different] the bonding electron pair will be shifted more towards the atom of greater electronegativity.

The electronegativity value of an atom is not a fixed quantity. Electronegativity value of an atom depends on the bonding situation. Different electronegativity values of an atom may be assigned in different bonding environment. So, electronegativity is not an inherent property of an atom.

Scales of Electronegativity

Different chemists have been defined the electronegativity term in different ways. Different chemists have proposed different scales of electronegativity.

Pauling’s Scale of Electronegativity

According to Pauling, electronegativity of an atom in a molecule is its power to attract the bonding electrons towards itself. A―A and B―B are two covalent molecules, react to form A―B covalent molecule---

A―A + B―B -----> A―B + A―B

According to Pauling, the bond dissociation energy of A―B covalent bond (E_A_―_B) is greater than the geometric mean of the bond dissociation energies of A―A (E_A_―_A) and B―B (E_B―B) covalent bonds, therefore---

E_A―B > √ (E_A―A x E_B―B)

The difference between E_A―B and [√(E_A―A x E_B―B)] is called ionic resonance energy of A―B bond. This ionic resonance energy is denoted by Δ_A―B. Therefore---

Δ_A―B = E_A―B – √(E_A―A x E_B―B)

Or, √(Δ_A―B) = √[E_A―B – √(E_A―A x E_B―B)] ----- (1)

Where, √Δ_A―B is a measure of ionic character in A―B covalent bond. The amount of ionic character in A―B covalent bond increases with the increase in the magnitude of √Δ_A―B. Therefore---

√(Δ_A―B) ∝ Amount of ionic character in A―B bond ----- (2)

Suppose, X_A is the electronegativity of A atom and X_B is the electronegativity of B atom. If the electronegativity of A atom is greater than the electronegativity of B atom, therefore, (X_A – X_B) value increases with the increases in the amount of ionic character in A―B bond. So--

(X_A – X_B) ∝ Amount of ionic character in A―B bond ----- (3)

From equation (2) and (3), we get---

(X_A – X_B) ∝ √(Δ_A―B)

Or, (X_A – X_B) = K √(Δ_A―B)

Where K is a constant.

Putting the value of [√(Δ_A―B)] from equation 1, we get---

(X_A – X_B) = K √[E_A―B – √(E_A―A x E_B―B)] ----- (4)

When bond dissociation energies are expressed in Kcal/mol, the equation (4) becomes---

(X_A – X_B) = 0.208 √[E_A―B – √(E_A―A x E_B―B)] ----- (5)

When bond dissociation energies are expressed in KJ/mol, the equation (4) becomes---

(X_A – X_B) = 0.102 √[E_A―B – √(E_A―A x E_B―B)] ----- (6)

Equation (5) and (6) are called the Pauling’s equation.

Pauling arbitrarily assumed the electronegativity of hydrogen, that is X_H is equal to 2.1 and calculate the electronegativity value of other atom with the help of these equation and framed his electronegativity scale---

Mulliken’s Approach

Mulliken proposed that the average of ionisation energy (IE) and electron affinity (EA) is proportional to the electronegativity (EN) of an element. Therefore---

EN ∝ [(IE + EA) / 2]

He proposed that when both IE and EA are in electron volt unit, the electronegativity can be calculated with the help of the following equation---

EN = 0.374 [(IE + EA) / 2] + 0.17

Or, EN = 0.187 [(IE + EA)] + 0.17

Though Mulliken’s approach is far-reaching, the main disadvantage is that, electron affinity values are not known except in a few cases.

Allred and Rochow’s Scale of Electronegativity

According to Allred and Rochow the electronegativity of an atom can be calculated by the following formula---

EN = [(0.359 x Z_eff) / r²] + 0.744

Or, EN = [{0.359 x (Z – σ)} / r²] + 0.744

Where---

Z_eff = Effective nuclear charge

Z = Nuclear charge

σ = Screening or shielding constant

r = Covalent radius in A⁰ unit

Periodic Variation of Electronegativity

Electronegativity increases on moving from left to right along a period with increase in nuclear charge. With increase in nuclear charge the radius of atom decreases, therefore electronegativity value increases.

Electronegativity decreases on moving from top to bottom along a group with increase in atomic radius.

Factors Affecting the Magnitude of Electronegativity

(1) Size of the atom---

Electronegativity ∝ 1/Atomic size

The tendency of smaller atom to attract the shared electrons towards itself is greater than larger atom. So, electronegativity increases with decrease in atomic size.

(2) Oxidation state---

Electronegativity ∝ Oxidation state

Higher oxidation state leads to greater electron attracting power, that is greater electronegativity. With increase in oxidation state atomic radius decrease, therefore electronegativity value increases.

Fe (1.80) < Fe²⁺ (1.83) < Fe³⁺ (1.96)

(3) Formal charge of an atom---

Electronegativity value of an atom in a compound is also affected by the formal charge on it. Electronegativity value increases with formal positive charge. Electronegativity value of nitrogen (N) in NH₄⁺ is higher than that in NH₃. Whereas electronegativity value decreases with formal negative charge. Electronegativity value of nitrogen (N) in NH₂^- is lower than that in NH₃.

(4) Nature of hybridisation---

The overall tendency of any bonded atom to attract electron is directly influenced by its bonding environment. Electronegativity is the property of the orbital of an atom. The property of an orbital is influenced by its state of hybridisation.

The order of penetration of atomic orbitals are---

s > p > d > f

Thus, the effective nuclear charge on s orbital should be greatest. Hence hybrid orbitals with greater s character should be more electronegative than hybrid orbitals with less s character. The order of electronegativity of hybrid orbitals is---

sp > sp² > sp³

(a) Compare the acidity of methane (CH₄), ethylene (C₂H₄) and acetylene (C₂H₂)---

The hybridisation of central carbon of methane (CH₄) is sp³, ethylene (C₂H₄) is sp², and acetylene (C₂H₂) is sp. Since the order of penetration are s > p > d > f, the hybrid orbitals with greater s character should be more electronegative than hybrid orbitals with less s character.

Methane (CH₄) : sp³: 25% s character

Ethylene (C₂H₄) : sp² : 33.3% s character

Acetylene (C₂H₂) : sp : 50% s character

Therefore, the order of acidity is---

CH₄ < C₂H₄ < C₂H₂

Due to enhanced electronegativity of carbon (C) atom in C₂H₂ and C₂H₄ molecules the electron pair involved in the formation of C―H bond is shifted more towards C-atom (C^δ-―H^δ+). As a result, when C―H bond gets broken, H atom is obtained as H⁺ ion. So, the formation of hydrogen ion (H⁺) in C₂H₂ and C₂H₄ explain the acidic nature of these molecules. Due to less electronegativity of C atom in CH₄ molecule the H atom remains neutral and CH₄ does not show acid character.

(b) Compare the basicities of R―NH₂, C₅H₅N and R―C≡N ---

The electronegativity of nitrogen (N) atom and the availability of N lone pair depends on its state of hybridisation. The electronegativity of N increases with increasing the s character in the hybrid orbitals and hence its basic character decreases.

R―NH₂ : N is sp³ hybridised

C₅H₅N : N is sp² hybridised

R―C≡N : N is sp hybridised

Therefore, R―NH₂ is fairly basic, C₅H₅N is feebly basic and R―C≡N has no basic property. So, the order of basic character is---

R―NH₂ > C₅H₅N > R―C≡N

(5) Nature of other atoms---

Electronegativity of an atom is influenced by the nature of other atoms with which it is attached. The electronegativity of carbon (C) atom is different in CH₃I and CF₃I. The C-atom is less electronegative than I-atom in CH₃I molecule. This creates a partial positive charge on C-atom and partial negative charge on I-atom. So CH₃I molecule represented as (CH₃)⁺I^-. On the other hand, in CF₃I molecule, due to presence of highly electronegative F-atom, C-atom becomes more electronegative than I-atom. So CF₃I molecule represented as (CF₃)^-I⁺.

Because of the difference in electronegativity of C-atom in CH₃I and CF₃I they hydrolysed in presence of OH^- differently.

CH₃⁺I^- + OH^- → CH₃OH + I^-

CF₃^-I⁺ + OH^- → CF₃H + OI^-

(6) Ionisation energy and Electron affinity---

Mulliken proposed that the average of ionisation energy (IE) and electron affinity (EA) is proportional to the electronegativity (EN) of an atom---

EN ∝ [(IE + EA) / 2]

So, the atom which have higher values of ionisation energy and electron affinity also have high values of electronegativity.

Fertilizer

2023-02-02T22:59:00.001+05:30

FERTILIZER

Sixteen elements are required for plant growth, these are carbon (C), hydrogen (H), oxygen (O), nitrogen (N), potassium (K), magnesium (Mg), calcium (Ca), phosphorus (P), sulphur (S), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), molybdenum (Mo) boron (B) and chlorine (Cl). Due to repeated cultivation soils get exhausted from these elements. So, for further cultivation and to make the land fertile, artificially prepared chemicals are used. So, fertilizers are the artificially prepared chemicals, which are mixed with the soil to make the land fertile for further cultivation. In other words, fertilizers are those substance which are mixed with the soil in order to remove the deficiency of essential elements required for plant growth.

Type of Fertilizer

(1) Complete fertilizer---

Fertilizers which supply all the essential elements, such as nitrogen (N), phosphorus (P) and potassium (K) [which are essential for plant growth] in varying proportion are known as complete fertilizer. Complete fertilizers are expressed as 6-12-12. This 6-12-12 signifying that, in this fertilizer, nitrogen (N) content by weight is 6%, phosphorus as P₂O₅ is 12% and potassium as K₂O is 12%. Examples of complete fertilizers are guano, nitro phosphate with added KCl etc.

(2) Incomplete fertilizer---

Fertilizers which supply one or two of the essential elements to the soil for plant growth are called incomplete fertilizer. Examples are super phosphate, nitro phosphate, calcium phosphate.

(3) Direct fertilizer---

Direct fertilizers are those, which can supply plants nutrients directly. Examples of direct fertilizers are super phosphates, nitrates and potassium salts.

(4) Indirect fertilizer---

Indirect fertilizers are those, which are used for improving physical and chemical properties of soil for better cultivation. Examples of indirect fertilizers are dolomite, lime, gypsum.

(5) Micro fertilizer---

Micro fertilizers are those, which can supply micronutrients such as calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), boron (B), copper (Cu) etc. Plants required these elements in very small quantities, but these elements are very essential for plant growth.

(6) Mixed fertilizer---

Fertilizers which can supply more than one essential element to the soil for plant growth are called mixed fertilizer. Examples are nitro phosphate, KNO₃, mixture of triple super phosphate and potassium sulphate.

Essential Requirement of a Fertilizer

Nitrogen (N), phosphorus (P) and potassium (K) are the essential nutrients for a plant growth, but every compound containing nitrogen (N), phosphorus (P) and potassium (K) cannot be used as a fertilizer. The essential requirement of a fertilizer is---

(i) The nutrient elements such as nitrogen, phosphorus and potassium etc present in the fertilizer compound in such a form that, they must be easily available to the plant.

(ii) The compound used as fertilizer, should be soluble in water.

(iii) The compound used as fertilizer should be stable, so that after a long time this made available to the plant.

(iv) The fertilizer compound should be non toxic for plant as well as human life.

(v) The compound used as a fertilizer should be cheaper.

(vi) The P^H of the fertilizer compound, is such that it can adjust the P^H of the soil.

(vii) Due to rain water, the fertilizer compound should be converted in such a form that, they must be easily available to the plant.

Nitrogenous Fertilizer

Nitrogenous fertilizers supply nitrogen (N) element to the soil. So, this type of fertilizers is called N-type fertilizers. Nitrogenous fertilizers are added to the soil in order to remove the deficiency of nitrogen in the soil. The fertilizing value of N-type fertilizers is expressed as available quantity of nitrogen present in them. Some examples of nitrogenous fertilizers are---

(i) Ammonium sulphate [(NH₄)₂SO₄]

(ii) Calcium cyanamide or Nitrolim [CaNCN]

(iii) Urea [CO(NH₂)₂]

(iv) Sodium nitrate [NaNO₃]

(v) Calcium ammonium nitrate [Ca(NO₃)₂.NH₄NO₃]

(vi) Ammonium sulphate nitrate [(NH₄)₂SO₄.2NH₄NO₃]

Phosphatic or Phosphorus Fertilizers

Phosphatic or phosphorus fertilizers supply phosphorus (P) element to the soil. So, this type of fertilizers is called P-type fertilizers. Phosphatic or phosphorus fertilizers are added to the soil in order to remove the deficiency of phosphorus in the soil. Some examples of P-type fertilizers are---

(i) Phosphate slag [Ca₃(PO₄)₂.CaSiO₃]

(ii) Super phosphate of lime [Ca(H₂PO₄)₂ + 2CaSO₄.2H₂O]

(iii) Triple super phosphate [Ca(H₂PO₄)₂]

Potassium Fertilizer

Potassium fertilizers supply potassium (K) element to the soil. So, this type of fertilizers is called K-type fertilizers. Potassium fertilizers are added to the soil in order to remove the deficiency of potassium in the soil. Some examples of K-type fertilizers are---

(i) Potassium sulphate [K₂SO₄]

(ii) Potassium chloride [KCl]

Fluorine

2023-01-30T23:04:00.000+05:30

FLUORINE

Symbol --- F

Abundance --- 0.065% in the earth’s crust

Allotropes --- alpha, beta

Physical state (STP) --- gas

Colour --- solid [alpha(opaque), beta(transparent)], liquid [bright yellow], gas [pale yellow]

Discovery --- A M Ampere

Atomic no --- 9

Atomic weight --- 18.998

Period --- 2

Group --- 17 or VIIA

Block --- p block

Known isotopes --- ₉F¹⁴, ₉F¹⁵, ₉F¹⁶, ₉F¹⁷, ₉F¹⁸, ₉F¹⁹, ₉F²⁰, ₉F²¹, ₉F²², ₉F²³, ₉F²⁴, ₉F²⁵, ₉F²⁶, ₉F²⁷, ₉F²⁸, ₉F²⁹, ₉F³⁰

Main isotope --- ₉F¹⁹

Isotopic abundance --- ₉F¹⁹ (100%)

Melting Point --- - 219 ⁰C (54 K) (F₂)

Boiling Point --- - 188 ⁰C (85 K) (F₂)

Triple Point --- 54 K, 90 kPa

Critical Temperature --- 144 K

Critical Pressure --- 5.17 MPa

Heat of Fusion --- 0.26 KJ/mol

Heat of Vaporisation --- 6.51 KJ/mol

Molar heat capacity (21 ⁰C) --- C_P [31 J/(mol-K)], C_V [23 J/(mol-K)]

Density --- 1.69 g/L (at STP)

Molar volume --- 0.0112

Electron configuration --- [He] 2s² 2p⁵

Electrons per shell --- 2 (1 st shell), 7 (2 nd shell)

Oxidation state --- -1

Valance --- 1

Electronegativity --- 4.0 (Pauling scale)

Electron affinity --- - 333 KJ/mol

Ionisation energy --- 1680 KJ/mol (1 st), 3375 KJ/mol (2 nd), 6148 KJ/mol (3 rd), 8406 KJ/mol (4 th)

Dissociation enthalpy --- 159 KJ/mol [F₂(gas)]

Covalent radius --- 64 pm

Van der Waals radius --- 135 pm

Atomic radius --- 42 pm

Ionic radius (6 – coord) --- 133 pm

F―F distance --- 143 pm

Natural occurrence --- primordial

Crystal structure --- cubic

Specific heat --- 824 J/(Kg K) (gas)

Thermal conductivity --- 0.025 W/(m K)

E⁰ (V) --- 2.9 [1/2 F₂+ e <==> F^-(aq)]

Magnetic type --- diamagnetic

Lattice angles --- π/2, π/2, π/2

Lattice constants --- 550 pm, 327 pm, 729 pm

Quantum numbers --- ²P_3/2

Neutron cross section --- 9.5 x 10^-3

Neutron mass absorption --- 2 x 10^-5

Refractive index --- 1.0001

Silicones

2023-01-29T19:50:00.000+05:30

SILICONES

A group of organosilicon polymers containing linkages of the type (---O―Si―O---) are called silicones. Generally, silicones are three types, such as linear silicones, cyclic silicones and cross-linked silicones.

Preparation of Silicones

Silicones are prepared in three steps, such as preparation of alkyl or aryl chlorosilanes, hydrolysis of alkyl or aryl chlorosilanes to produced silanols and polymerization of silanols.

(1) At first, alkyl or aryl chlorosilanes are prepared by the following way---

(i) When alkyl or aryl chloride (R―Cl) are heated with silicon (Si) at 300 ⁰C in presence of Cu catalyst, mixture of alkyl or aryl chlorosilanes are produced.

2R―Cl + Si ----> RSiCl₃ + R₂SiCl₂ + R₃SiCl

(ii) Reaction of Grignard reagent (R―MgCl) with SiCl₄ produced alkyl or aryl chlorosilanes.

R―MgCl + SiCl₄ ----> RSiCl₃ + MgCl₂

2R―MgCl + SiCl₄ ----> R₂SiCl₂ + 2MgCl₂

3R―MgCl + SiCl₄ ----> R₃SiCl + 3MgCl₂

(2) Hydrolysis of alkyl or aryl chlorosilanes to produced silanols----

When alkyl or aryl chlorosilanes treated with water, silanols are produced.

RSiCl₃ + 3H₂O ----> RSi(OH)₃ + 3HCl

R₂SiCl₂ + 2H₂O ----> R₂Si(OH)₂ + 2HCl

R₃SiCl + H₂O ----> R₃SiOH + HCl

(3) Polymerisation of Silanols---

In the polymerisation process some molecules of H₂O are removed and form various types of silicones such as linear, cyclic or cross linked according to the nature of the alkyl or aryl hydroxy (silanols) derivatives----

(i) Linear silicones---

Polymerisation of dialkyl dihydroxy silane [R₂Si(OH)₂] gives rise to straight chain linear silicone polymers and as an active OH group is left at each end of the chain, polymerisation continues and the chain increases in length. Thus dialkyl dihydroxy silane [R₂Si(OH)₂] is a chain building unit. High polymers are obtained in this way. The structure of linear silicone polymer is as follows---

(ii) Cyclic silicones---

Careful polymerisation of dialkyl dihydroxy silane [R₂Si(OH)₂] can produced cyclic silicone structure containing three, four, five or six silicon (Si) atoms. The structure of cyclic silicone polymer is as follows--

(iii) Cross linked silicones---

Polymerisation of alkyl trihydroxy silane [RSi(OH)₃] gives rise to cross linked two dimensional silicone polymers and as an active OH group is left at each end of the chain, polymerisation continues and chain increases in length. The structure of cross linked silicone polymer is as follows---

Polymerisation of trialkyl monohydroxy silane [R₃SiOH] gives rise to linear straight chain silicone dimer. The structure of silicone dimer is as follows---

Trialkyl monohydroxy silane [R₃SiOH] is used as a chain blocking unit. When some trialkyl monohydroxy silane [R₃SiOH] is mixed with dialkyl dihydroxy silane [R₂Si(OH)₂], the trialkyl monohydroxy silane [R₃SiOH] will block the chain produced by dialkyl dihydroxy silane [R₂Si(OH)₂].

Some Important Silicones

(1) High thermal silicones---

When hydrolysis of alkyl or aryl chlorosilanes is carried out in presence of aluminium halides, titanium halides, aluminium alkoxides or titanium alkoxides two dimensional linear or cyclic high thermal silicone polymer is obtained in which some silicon (Si) atoms are replaced by aluminium (Al) or titanium (Ti) atoms. The presence of Al or Ti atoms in the silicone polymer structure, increases the thermal stability of the polymer. This silicone polymer has exceptionally high thermal stability. The structure of high thermal silicone polymer is as follows---

(2) Silicone oil---

When some trialkyl monohydroxy silane [R₃SiOH] is mixed with dialkyl dihydroxy silane [R₂Si(OH)₂], silicone oil is obtained. It has low temperature coefficient of viscosity, high thermal stability and good insulating properties. The structure of silicone oil is as follows---

(3) Silicone rubbers---

Silicone rubbers are long chain polymer, with some cross linking between the chains. These rubbers retain its elasticity and shape even after vulcanization.

Properties and Uses of Silicones

Silicones are thermally stable, chemically inert, excellent water repellent, good electrical insulator and non toxic. They are resistance to oxidation and most chemicals such as acids, alkalies etc due to their chemical inertness. Their inertness is due to their stable silica like skeleton and high strength of Si―C bonds. They have non stick properties.

They are used in making waterproof cloth, in lubrication, as insulating materials, as antifoams, in cosmetics, as stop cock grease, in electric motor and other electric appliances, as hydraulic fluids, as dielectric fluids etc.

Borax

2023-01-25T18:30:00.000+05:30

BORAX

Salts of boric acids (H₃BO₃) are called borates. Borax is an important borate. Borax is a sodium salt of tetraboric acid (H₂B₄O₇). Ten molecules of water, as water of crystallization are present in borax compound. So, borax is sodium tetraborate decahydrate [Na₂B₄O₇.10H₂O].

Preparation of Borax

(1) Borax from boric acid (H₃BO₃) ---

(i) Borax is obtained, when boric acid (H₃BO₃) is boiled with sodium carbonate (Na₂CO₃) solution-

4H₃BO₃ + Na₂CO₃ = Na₂B₄O₇ + CO₂ + 6H₂O

(ii) Borax is obtained, when boric acid (H₃BO₃) is boiled with excess sodium hydroxide (NaOH) solution---

4H₃BO₃ + 2NaOH + 3H₂O = Na₂B₄O₇.10H₂O

(2) Borax from colemanite (2CaO, 3B₂O₃) ---

Borax is obtained, when colemanite (2CaO, 3B₂O₃) is boiled with sodium carbonate (Na₂CO₃) solution ---

2CaO, 3B₂O₃ + 2Na₂CO₃ = Na₂B₄O₇ + 2NaBO₂ + 2CaCO₃

At first, precipitate calcium carbonate (CaCO₃) is filtered out and then concentrated the remaining filtrate. As a result, crystals of borax are deposited. NaBO₂ present in the mother liquor is converted to borax by passing CO₂.

4NaBO₂ + CO₂ = Na₂B₄O₇ + Na₂CO₃

Structure of Borax

The crystal structure study of borax has indicated that, two H₂O molecules participate in the formation of borax anion. So, borax is now represented as----

Na₂[B₄O₅(OH)₄].8H₂O

The anion of borax [B₄O₅(OH)₄]^2- is made up of two trigonal planer BO₃ units and two tetrahedral BO₄ units. The B atom of BO₃ unit is sp² hybridised and each B atom of BO₃ unit forms three B―O sigma(σ) bonds. The B atom of BO₄ unit is sp³ hybridised. one extra electron is present in each BO₄ units and each B atom of BO₄ unit forms four B―O sigma (σ) bonds. Four OH groups linked with four B atoms. A bridge bond is formed among two B atoms and one O atom. So, the structure of the borax anion [B₄O₅(OH)₄]^2- is as follows---

Properties of Borax

White crystalline solid borax exists in three different crystal structure.

(1) Monoclinic or prismatic borax---

The formula of monoclinic or prismatic borax is Na₂B₄O₇.10H₂O, it is the most common form of borax.

(2) Octahedral or jeweller’s borax---

The formula of octahedral or jeweller’s borax is Na₂B₄O₇.5H₂O. The octahedral form of borax (Na₂B₄O_7.5H₂O) is obtained, when monoclinic form of borax (Na₂B₄O₇.10H₂O) is heated above 60⁰C.

(3) Borax glass or anhydrous borax----

The formula of borax glass or anhydrous borax is Na₂B₄O₇. The anhydrous borax (Na₂B₄O₇) is obtained when monoclinic form of borax (Na₂B₄O₇.10H₂O) is heated above its melting point.

In water borax gets hydrolysed, and gives a mixture of strong base NaOH and weak acid H₃BO₃. Since boric acid (H₃BO₃) is weak so, the aqueous solution of borax is alkaline.

Na₂B₄O₇ + 7H₂O <=====> 2NaOH + 4H₃BO₃

On heating borax first swells losing water molecules. On further heating it gives NaBO₂ and B₂O₃. A glassy bead is formed.

Na₂B₄O₇.10H₂O = 2NaBO₂ + B₂O₃ + 10H₂O

Borax bead test-----

When this glassy bead (B₂O₃) is heated strongly with coloured metal salts, specific coloured beads are obtained. This offers a means of identifying certain metal ions like Cu, Co, Cr, Ni, Fe etc.

CuSO₄ = CuO + SO₃

CuO + B₂O₃ = Cu(BO₂)₂

This gives green colour in hot condition and blue colour in cold condition.

When this Cu(BO₂)₂ is again heated in reducing flame it becomes dull red and opaque.

2Cu(BO₂)₂ (Cu = +2) + C ----> 2CuBO₂ (Cu = +1) + B₂O₃ + CO

2CuBO₂ (Cu = +1) + C ----> 2Cu (Cu = 0) + B₂O₃ + CO

Reaction of borax with conc HCl or H₂SO₄ forms boric acid---

Na₂B₄O₇ + 2HCl + 5H₂O = 2NaCl + 4H₃BO₃

Na₂B₄O₇ + H₂SO₄ + 5H₂O = Na₂SO₄ + 4H₃BO₃

When borax is heated with ammonium chloride, boron nitride is formed---

Na₂[B₄O₅(OH)₄] + 2NH₄Cl ----> 2NaCl + 2BN + B₂O₃ + 6H₂O

Uses of Borax

Borax is used in the manufactured of enamels, washing powders, various types of glasses such as optical and hard glasses. Borax is also used in making antiseptic.

Oxygen

2023-01-18T22:25:00.002+05:30

OXYGEN

Symbol --- O

Abundance --- most abundant element, 46% in the earth’s crust, 21% by volume in air, 89% by weight of the water in the oceans.

Allotropes --- atomic oxygen [O(³P)], dioxygen (O₂), ozone (O₃), tetraoxygen (O₄), solid oxygen.

Physical state --- gas

Colour --- colourless gas

Discovery --- C W Scheele

Atomic no --- 8

Atomic weight --- 15.999

Period --- 2

Group --- 16 or VIA

Block --- p block

Known isotopes --- ₈O¹², ₈O¹³, ₈O¹⁴, ₈O¹⁵, ₈O¹⁶, ₈O¹⁷, ₈O¹⁸, ₈O¹⁹, ₈O²⁰, ₈O²¹, ₈O²², ₈O²³, ₈O²⁴

Main isotopes --- ₈O¹⁶, ₈O¹⁷, ₈O¹⁸

Isotopic abundance --- ₈O¹⁶ (99.763%), ₈O¹⁷ (0.037%), ₈O¹⁸ (0.2%)

Melting Point --- - 219 ⁰C (54 K) (dioxygen)

Boiling Point --- - 183 ⁰C (90 K) (dioxygen)

Triple Point --- 54 K, 0.14 kPa

Critical Temperature --- 154 K

Critical Pressure --- 5.04 MPa

Heat of Fusion --- 0.44 KJ/mol (dioxygen)

Heat of Vaporisation --- 6.81 KJ/mol (dioxygen)

ΔH⁰_{(atomization)} --- 247 KJ/mol

Molar heat capacity --- 29.37 J/(mol-K) (dioxygen)

Density --- 1.41 g/L (at STP)

Molar volume --- 0.0111

Electron configuration --- [He] 2s² 2p⁴

Electrons per shell --- 2 (1 st shell), 6 (2 nd shell)

Oxidation state --- -2, -1

Valance --- 2

Electronegativity --- 3.44 (Pauling scale)

Electron affinity --- 1.41 KJ/mol

Ionisation energy --- 1314 KJ/mol (1 st), 3388 KJ/mol (2 nd), 5300.3 KJ/mol (3 rd), 7469.1 KJ/mol (4 th)

Covalent radius --- 66 pm

Van der Waals radius --- 152 pm

Atomic radius --- 48 pm

Natural occurrence --- primordial

Crystal structure --- cubic

Specific heat --- 918.5 J/(Kg K) (gas)

Thermal conductivity --- 0.026 W/(m K)

Speed of sound --- 330 m/s (gas)

Magnetic type --- paramagnetic

Mass magnetic susceptibility --- 1.33 x 10^-6 m³/Kg

Molar magnetic susceptibility --- 4.27 x 10^-8 m³/mol

Volume magnetic susceptibility --- 1.9 x 10^-6

Lattice angles --- π/2, 2.31, π/2

Lattice constants --- 540.1 pm, 342.8 pm, 508.5 pm

Quantum numbers --- ³P₂

Neutron cross section --- 2.8 x 10^-4

Neutron mass absorption --- 1 x 10^-6

Refractive index --- 1.0002

Polythene or Polyethylene

2023-01-16T18:39:00.000+05:30

POLYTHENE or POLYETHYLENE

Polythene or polyethylene is very useful and one of the most common polymers today. Polythene or polyethylene is prepared from pure ethylene (pure ethylene obtained from petroleum) by polymerization process either by high pressure method or by low pressure method. Polythene or polyethylene which is manufactured by high pressure method possesses a low density, hence this type of polythene or polyethylene is known as high pressure polythene or low density polythene. Polythene or polyethylene which is manufactured by low pressure method possesses a high density, hence this type of polythene or polyethylene is known as low pressure polythene or high density polythene.

High Pressure Method

When polythene or polyethylene is synthesized by high pressure method a free radical yielding catalyst such as oxygen or peroxide is required.

Ethylene with highly pure quality is polymerized at a pressure of 1000 – 1500 atm and at temperature of 250 ⁰C in the presence of a free radical yielding catalyst. From the reactor, the molten liquid passes to a separator. In the separator the unreacted ethylene is removed and recycled. So, now in the separator molten liquid is water white polythene or polyethylene. This can be extruded, chilled and solidified, chopped and stored. By adding fillers and colouring matter to the molten polymer, moulding powder can be prepared.

Since polythene or polyethylene prepared by high pressure method possesses a low density, so this type of polythene or polyethylene are highly branched, consists of several short and long branches, as shown in the following structure----

High pressure polythene or low-density polythene is extremely poor conductor of electricity, chemically inert, tough, flexible over a wide range of temperature. This type of polythene or polyethylene is not attacked by acids, alkalies or oil.

High pressure polythene or low density polythene is used for the fabrication of king toys, making pipes, making containers, wires and cable insulation, in films, in packings, articles of domestic use, making bottles.

Low Pressure Method

When polythene or polyethylene is synthesized by low pressure method a metal derived catalyst is required. Some examples of metal derived catalyst are titanium tetrachloride in a hexane solution of aluminium triethyl, chromium oxide on a silica alumina support etc.

Ethylene with highly pure quality and cyclohexane solvent along with a suitable metal derived catalyst are fed to a reactor. Here cyclohexane solvent serves for several purpose such as----

Cyclohexane solvent acts as a medium for dissipating the heat of reaction.

Cyclohexane solvent controls the rate of consumption of ethylene.

Cyclohexane solvent protects the growing polymer from chain breaks.

In the reactor under 35 atm pressure and at a temperature of 60 – 200 ⁰C ethylene is polymerized. From the reactor, the molten liquid passes to a flash drum. In the drum excess cyclohexane and unreacted ethylene are removed. The polymer produced due to polymerization of ethylene is then centrifuged and filtered. The polymer which is ash free thus obtained, is precipitated from the solution in a stripper to get a slurry. By floatation, the slurry is separated from water. It is then dried and finished.

Since polythene or polyethylene prepared by low pressure method possesses a high density, so this type of polythene or polyethylene molecules contains linear unbranched chains. These chains can be close packed in the solid state. Due to this close packing, this type of polythene or polyethylene has high density.

Low pressure polythene or high density polythene is more stronger, chemically more inert, more stiffer and harder than low density polythene.

High density polythene possesses high softening temperature and greater tensile strength.

Low pressure polythene or high density polythene is used for making toys, bottles, containers etc. This polythene is also used in the injection moulding of house wares.

Paints and Pigments

2023-01-13T23:09:00.000+05:30

PAINTS and PIGMENTS

Paints are liquid substances, which hold solid colouring material suspension, known as pigments. These stable mechanical mixtures can be applied evenly to a surface for protective purpose, decorative purpose or both.

Essential ingredients of paints are---

Pigments

Various inorganic or organic insoluble substances which are widely used in surface coatings are known as pigments. Pigments are naturally occurring or manufactured and the colour of the paint depends upon the colour of the pigments.

The important properties of pigments are---

(1) Good covering power.

(2) Good mixing ability with oil.

(3) Opacity

(4) Chemical inertness of pigments.

(5) Toxicity level of pigments are very low or nil.

(6) High hiding power.

(7) High limiting strength.

(8) Pigments reflect the destructive UV light and protect the film.

Extenders or Fillers

Extenders or fillers are inert solid substances. Some examples of extenders or fillers are talc, BaSO₄, china clay, asbestos etc. In order to decrease the cost of the paints and to supplement the pigments in increasing the covering and weathering power of the film, the extenders or fillers are added to the paint. Extenders or fillers improve the consistency, levelling, durability and setting of the paints.

Driers

In order to accelerate the drying of the film through oxidation and polymerization, certain driers also been used in the paint. The polymerization of the unsaturated drying oils occurs by a reaction mechanism which involves peroxide intermediate. Due to catalytic activity of the drier they act as a catalyst and promoters in the oxidation polymerization process. Driers are generally mixed with hot boiled linseed oil. Driers dissolve in the hot oil and they reduced the drying time. Some examples of driers are Co, Mn, Pb, cobalt linoleates, cobalt tungstates, MnO₂, litharge, lead acetate, manganese acetate etc.

Thinners or Diluents

In order to dissolve film forming material and to thin concentrated paints for better handling, thinners or diluents is also added to the paints. Some examples of thinners or diluents are petrol, benzene, naphtha, rosin spirit etc.

Film Forming Materials

The film forming materials acts as carriers for the pigments.

Antiskinning Agents

Certain antiskinning agents such as polyhydroxy phenols are added to the paint in order to prevent gelting and skinning of the finished product.

Plasticizer

Plasticizers are added to the paint, in order to reduce certain aspects of cracking in paints.

Resins

A variety of resins are also added to the paints.

Classification of pigments

According to the colour of the pigments, they are classified in the following types---

(A) White Pigments------

(i) White lead [Pb(OH)₂.2PbCO₃]

(ii) Zinc oxide [ZnO]

(iii) Titanium dioxide [TiO₂]

(iv) Lithopone [BaSO₄ + ZnS]

(B) Blue Pigments----

(i) Ultramarine

(ii) Cobalt blue

(iii) Iron blue

(C) Red Pigments----

(i) Red lead [Pb₃O₄]

(ii) Cadmipone [CdS + BaSO₄]

(iii) Iron oxide [Fe₂O₃]

(iv) Chrome red [Pb(OH)₂.PbCrO₄]

(D) Black Pigments-----

(i) Carbon black

(ii) Furnace black

(iii) Lamp black

(E) Green Pigments----

(i) Chrome green [Cr₂O₃]

(ii) Malachit green [Cu(OH)₂.CuCO₃]

(iii) Rinman’s green [CoO.ZnO]

(F) Orange Pigments----

(i) Cadmium orange

(ii) Basic lead chromate

(G) Yellow Pigments----

(i) Lead chromates

(ii) Zinc chromates

(iii) Litharge

(iv) Ocher [A naturally occurring pigment]

(H) Brown Pigments----

(i) Burnt umber

(ii) Burnt sienna

(I) Metallics Pigments----

(i) Zinc dust

(ii) Copper powder

(J) Metal Protective Pigments----

(i) Zinc and basic lead

(ii) Red lead

Due to durability and colouring power of toners (insoluble organic dye), they are also used directly as pigments.

Lakes are organic dyes on an inorganic absorbent, have also been used as pigments.

Requisites of a good paint

(i) Paint should be resistant to heat and light.

(ii) Due to small change of temperature, the colour of paint should not fade.

(iii) Due to exposing to light, the colour of paint should not fade.

(iv) Paint should be resistant to the corrosive action of acids and bases.

Nitrogen

2023-01-11T20:36:00.003+05:30

NITROGEN

Symbol --- N

Abundance --- 0.002% in earth’s crust, 78% by volume and 75% by weight in air.

Allotropes --- dinitrogen (N≡N)

Physical state --- gas

Colour --- colourless gas

Discovery --- Daniel Rutherford

Atomic no --- 7

Atomic weight --- 14.007

Period --- 2

Group --- 15 or VA

Block --- p block

Known isotopes --- ₇N¹¹, ₇N¹², ₇N¹³, ₇N¹⁴, ₇N¹⁵, ₇N¹⁶, ₇N¹⁷, ₇N¹⁸, ₇N¹⁹, ₇N²⁰, ₇N²¹, ₇N²²

Main isotopes --- ₇N¹⁴, ₇N¹⁵

Isotopic abundance --- ₇N¹⁴ (99.58%), ₇N¹⁵ (0.34%)

Melting Point --- - 210 ⁰C (63 K)

Boiling Point --- - 196 ⁰C (77 K)

Triple Point --- 63 K, 12.5 kPa

Critical Temperature --- 126 K

Critical Pressure --- 3.38 MPa

Heat of Fusion --- 0.71 KJ/mol (dinitrogen)

Heat of Vaporisation --- 5.56 KJ/mol (dinitrogen)

ΔH⁰_{(atomization)} --- 473 KJ/mol

Molar heat capacity --- 29.12 J/(mol-K) (dinitrogen)

Density --- 1.25 g/L (at 0 ⁰C)

Molar volume --- 0.0111

Electron configuration --- [He] 2s² 2p³

Electrons per shell --- 2 (1 st shell), 5 (2 nd shell)

Oxidation state --- -3, -2, -1, 0, +1, +2, +3, +4, +5

Valance --- 3

Electronegativity --- 3.04 (Pauling scale)

Electron affinity --- 7 KJ/mol

Ionisation energy --- 1403 KJ/mol (1 st), 2855 KJ/mol (2 nd), 4577 KJ/mol (3 rd), 7475.5 KJ/mol (4 th)

Covalent radius --- 71 pm

Van der Waals radius --- 155 pm

Atomic radius --- 56 pm

Natural occurrence --- primordial

Crystal structure --- hexagonal

Specific heat --- 1039 J/ (Kg K) (gas)

Thermal conductivity --- 0.025 W/ (m K)

Speed of sound --- 353 m/s (gas)

Magnetic type --- diamagnetic

Mass magnetic susceptibility --- -5.3 x 10^-9 m³/Kg

Molar magnetic susceptibility --- -1.5 x 10^-10 m³/mol

Volume magnetic susceptibility --- -6.7 x 10^-9

Lattice angles --- π/2, π/2, 2π/3

Lattice constants --- 385.9 pm, 385.9 pm, 626.3 pm

Quantum numbers --- ⁴S_3/2

Neutron cross section --- 1.9

Neutron mass absorption --- 4.8 x 10^-3

Refractive index --- 1.0002

Carbocation

2023-01-10T18:39:00.001+05:30

Carbocation

When an organic species containing a carbon atom and that carbon atom bearing only three electron pairs, means six electrons is called a carbocation. Carbocation containing a positive charge and the carbon atom of the carbocation is sp² hybridized. The carbon atom of the carbocation uses its three hybrid orbitals for forming three sigma bonds with three substituents and the remaining p orbital remains vacant. The structure of carbocation is flat structure, having all the three covalent bonds in one plane. The bond angles between these covalent bonds are 120⁰.

Formation of Carbocation

Carbocation can be formed in a number of ways. Some of these reactions by which carbocations are generated are summarized below---

(1) Carbocation is formed by the solvolysis of C―X bond (where X = halogen such as F, Cl, Br, I or OBs etc) ---

R―X -----> R⁺ + X^-

(2) When alkyl halide (R―X) reacts with superacids such as SbF₅, HSO₃F etc, carbocation is formed --

R―F + SbF₅ -----> R⁺ + SbF₆^-

(3) When acetyl chloride (R―CO―Cl) reacts with aluminium chloride (AlCl₃) carbocation is generated---

R―CO―Cl + AlCl₃ ----> R―C⁺=O + AlCl₄^-

(4) When nitrous acid (HNO₂) reacts with amine (R―NH₂), carbocation is produced--

R―NH₂ + HNO₂ ------> R⁺ + N₂ + H₂O + OH^-

(5) Protonation of alcohol (R―OH) by acid, followed by dehydration produced carbocation-

R―OH + H⁺ -----> R―OH₂⁺

R―OH₂⁺ -----> R⁺ + H₂O

(6) When carbonyl compound reacts with H⁺, carbocation is formed----

R―CO―R + H⁺ -----> R₂C⁺―OH

(7) When alkene reacts with H⁺, carbocation is formed----

R―CH=CH₂ + H⁺ -----> R―CH⁺―CH₃

(8) When allyl halide reacts with Ag⁺, allyl carbocation is formed----

CH₂=CH-CH₂-Br + Ag⁺ ---> CH₂=CH-CH₂⁺ + AgBr

(9) When benzyl halide reacts with Ag⁺, benzyl carbocation is formed-----

Ph―CH₂―Br + Ag⁺ ----> Ph―CH₂⁺ + AgBr

Classification of Carbocation

Carbocations are classified into three categories----

Primary Carbocation

When a positively charged carbon ion linked with another carbon atom, then this carbocation is called primary carbocation.

CH₃―CH₂⁺

Secondary Carbocation

When a positively charged carbon ion linked with other two carbon atoms, then this carbocation is called secondary carbocation.

CH₃―CH⁺―CH₃

Tertiary Carbocation

When a positively charged carbon ion linked with other three carbon atoms, then this carbocation is called tertiary carbocation.

Stability of Carbocation

The relative stabilities of the alkyl substituted carbocations are----

R₃C⁺ > R₂CH⁺ > RCH₂⁺ > CH₃⁺

The stabilities of the alkyl substituted carbocations can be explained by various factors, which are---

Inductive Effect

The alkyl groups have +I effect, so they tend to release electrons and partially compensate for the electron deficiency of the positively charged carbon. When the number of alkyl groups attached to the positively charged carbon atom increases, electrons release by this alkyl groups increases and partially compensate for the electron deficiency of the positively charged carbon also increases. So, the stability of tertiary carbocation (containing three alkyl groups) is greater than secondary carbocation (containing two alkyl groups). The stability of secondary carbocation is greater than primary carbocation (containing only one alkyl group). The stability of primary carbocation is greater than methyl carbocation (containing no alkyl group).

Hyperconjugation

The sigma (σ) electrons of an alpha (α) C―H bond can be delocalized into the unfilled ‘p’ orbital of the positively charged carbon atom. Thus, spreading the charge over all such bonds. So, several hyper conjugative resonance structure can be drawn for alkyl substituted carbocation and each of these resonance structure containing same number of covalent bonds as the first structure.

For primary carbocation three structure are drawn, for secondary carbocation six structure are drawn and for tertiary carbocation nine structure are drawn. With increase the number of hyper conjugative resonance structure, the stabilities of the carbocation increases.

Mesomeric Effect or Resonance Effect

The stabilities of conjugated carbocations can be explained by mesomeric effect or resonance effect. Resonance enhances the stability of a carbocation by delocalization of its charge in conjugated system like allyl or benzyl carbocation. More number of resonating structures of a carbocation, more will be its stability. The order of stability of allyl and benzyl carbocations are----

CH₂=CH-CH₂⁺<Ph-CH₂⁺<(Ph)₂CH⁺<(Ph)₃C⁺

Number of resonating structures of allyl carbocation is 2, whereas number of resonating structures of Ph―CH₂⁺ is 5, (Ph)₂CH⁺ is 9 and (Ph)₃C⁺ is 13.

Steric Effect

When carbocations derived from highly substituted substrate, steric effects play an important role in the formation and stability of carbocations. Here steric relief is the key factor for the formation and stability of carbocations. Tri-isopropyl chloride is a highly substituted substrate. In tri-isopropyl chloride three bulky isopropyl groups are pushed together due to sp³ angle of 109⁰28'. So due to this pushing together, there arises a strain called B-strain. When the substrate tri-isopropyl chloride ionizes, the angle expands from 109⁰28' to 120⁰. So, a relief in strain arises due to this angle expands and space between alkyl groups (isopropyl groups) increases.

Nylon 6.6

2023-01-05T19:03:00.001+05:30

Nylon 6.6

Nylon 6.6 is a diamine-dibasic acid polymer. Nylon 6.6 is generally prepared by the reaction of hexamethylene diamine [H₂N―(CH₂)₆―NH₂] and adipic acid [HOOC―(CH₂)₄―COOH]. In nylon 6.6 first 6 indicates the number of carbon atoms in the hexamethylene diamine part and second 6 indicates the number of carbon atoms in the adipic acid part. Since this polyamide contain 6 carbon atoms in the first part and 6 carbon atoms in the second part, so, it is nylon 6.6.

Manufacture of Adipic Acid

Adipic acid is prepared by various synthetic methods. Among these various synthetic methods, two such methods are----

Synthetic Method – 1

Adipic Acid from Phenol

Reaction of phenol with hydrogen in presence of powdered Ni catalyst at 160 – 170 ⁰C formed cyclohexanol. Oxidation of cyclohexanol in presence of Cu at 250 ⁰C produced cyclohexanone. When cyclohexanone treated with 6% HNO₃ at 85 – 90 ⁰C adipic acid is formed.

Synthetic Method – 2

Adipic Acid from Benzene

Reaction of benzene with hydrogen in presence of powdered Raney Ni catalyst at 180 – 250 ⁰C and at 10 – 60 atm formed cyclohexane. Oxidation of cyclohexane in presence of air at 125 ⁰C and in presence of Mn, Co catalyst produces cyclohexanol and cyclohexanone. When this mixture of products reacted with 40% HNO₃ at 80 – 85 ⁰C adipic acid is formed.

Manufacture of Hexamethylene diamine

Hexamethylene diamine is prepared by various synthetic methods. Among these various synthetic methods, three such methods are----

Synthetic Method – 1

Hexamethylene diamine from Butadiene

Reaction of butadiene with chlorine produced 1,4-dichlorobut-2-ene. When this 1,4-dichlorobut-2-ene treated with KCN in presence of CuCl at 80 – 85 ⁰C 1,4-dicyanobut-2-ene is formed. Reaction of 1,4-dicyanobut-2-ene with hydrogen in presence of Pd-C produced adiponitrile. When adiponitrile treated with hydrogen at high pressure in presence of NH₃ hexamethylene diamine is formed.

Synthetic Method – 2

Hexamethylene diamine from Adipic Acid

Reaction of adipic acid with NH₃ at 350 – 400 ⁰C in silica gel produced adipamide. This adipamide heated to formed adiponitrile. Reaction of adiponitrile with hydrogen in presence of NH₃ at high pressure produced hexamethylene diamine.

Synthetic Method – 3

Hexamethylene diamine from Acrylonitrile

Reaction of acrylonitrile with hydrogen at law pressure produced adiponitrile. When adiponitrile treated with hydrogen in presence of Co-Cu at 100 – 135 ⁰C produced hexamethylene diamine.

Manufacture of nylon 6.6

Adipic acid and hexamethylene diamine both are soluble in water. So, aqueous solution of both reactants is mixed in 1:1 molar ratio, and maintain 7.8 P^H of the mixture. The solution is evaporated under vaccum. 0.5 – 1 % mole of CH₃COOH as viscosity and molecular weight stabilizer is added to the liquid residue, and the liquid residue charged to an autoclave under 250 poise pressure and heated at about 270 – 280 ⁰C. Vaccum is applied after some progress of the reaction to facilitate to release and removal of the rest water from the reaction zone. After 3 – 4 hours, the process has been completed. By a nitrogen pressure of 40 -50 poise, the molten polymer is extruded through the bottom of the autoclave as a ribbon with molecular weight ranging between 12000 – 16000, which after cooling by water and air in the particular stages, is cut into cubes of regular sizes.

Properties of nylon 6.6

Nylon 6.6 is tough, strong, and elastic in nature. Nylon 6.6 possess high tensile strength and abrasion resistance. Its moisture resistance is very good and it maintain its elasticity upto 150 ⁰C. Melting point of nylon 6.6 is 263 ⁰C in nitrogen and in air is 250 ⁰C. Specific gravity of nylon 6.6 is 1.14. Strength and abrasion resistance of nylon 6.6 is high and it maintain its toughness upto 150 ⁰C and its solvent resistance is good. Nylon 6.6 attacked by air or water at elevated temperature and it is opaque to sunlight. In sunlight nylon 6.6 undergoes fading in colours.

Carbon

2023-01-02T21:14:00.001+05:30

Carbon

Symbol --- C

Abundance --- 0.8% in earth’s crust

Allotropes --- diamond, graphite, fullerenes, graphene, carbon nanotube, carbon nanobud, amorphous carbon, lonsdaleite (hexagonal diamond), diamane, AA’-graphite

Physical state --- solid

Colour --- diamond (transparent), graphite (black),

Discovery --- Egyptians and Sumerians

Atomic no --- 6

Atomic weight --- 12.011

Period --- 2

Group --- 14 or IVA

Block --- p block

Known isotopes --- ₆C¹⁰, ₆C¹¹, ₆C¹², ₆C¹³, ₆C¹⁴, ₆C¹⁵, ₆C¹⁶, ₆C¹⁷, ₆C¹⁸, ₆C¹⁹, ₆C²⁰

Main isotopes --- ₆C¹², ₆C¹³, ₆C¹⁴

Isotopic abundance --- ₆C¹² (98.8%), ₆C¹³ (1.1%), ₆C¹⁴ (trace) (t_1/2 = 5570 years)

Melting Point --- 4000 K (diamond at 125 kbar), 4000 K (graphite at 9 kbar)

Density --- diamond (3.51 g/cm³), graphite (2.26 g/cm³), amorphous carbon (1.9 g/cm³)

Electron configuration --- [He] 2s² 2p²

Electrons per shell --- 2 (1 st shell), 4 (2 nd shell)

Oxidation state --- +4

Valance --- 4

Electronegativity --- 2.5 (Pauling scale)

Electron affinity --- 152.3 KJ/mol

Ionisation energy --- 1086 KJ/mol (1 st), 2352 KJ/mol (2 nd), 4619 KJ/mol (3 rd), 6221 KJ/mol (4 th)

Covalent radius --- 77 pm (sp³), 72.5 pm (sp²), 69 (sp)

Van der Waals radius --- 169.8 pm

Crystal structure --- diamond (transparent) face centered cubic, graphite (black) hexagonal

Molar heat capacity --- diamond [6.15 J/(mol-K)], graphite [8.51 J/(mol-K)]

Specific heat --- graphite 710 J/ (Kg K)

Thermal expansion --- diamond [0.8 μm/ (m K)]

Thermal conductivity --- diamond [900-2300 W/ (m K)]

Speed of sound --- diamond (18345 m/s)

Magnetic type --- diamagnetic

Lattice angles --- π/2, π/2, 2π/3

Lattice constants --- 246.3 pm, 246.3 pm, 670.9 pm

Quantum numbers --- ³P₀

Neutron cross section --- 0.0035

Neutron mass absorption --- 1.5 x 10^-5

Electrical resistivity --- graphite (7.8 μΩ.m)

Mohs hardness --- diamond (10)

graphite (1-2)

Young’s modulus --- diamond (1050 GPa)

Shear modulus --- diamond (475 GPa)

Bulk modulus --- diamond (440 GPa)

Poisson ratio --- diamond (0.1)

Refractive index (546 nm) --- diamond (2.41), graphite (2.15)

Urea

2023-01-01T21:31:00.001+05:30

Urea

Urea is the most important nitrogenous fertilizer contain about 45 – 47% of nitrogen.

Raw Materials

The raw materials required for the manufacture process of urea are carbon di oxide (CO₂) and ammonia (NH₃).

Manufacture Process

The following steps are used for the manufactured of urea---

Through a silver lined special autoclave, liquid carbon di oxide (CO₂) and liquid ammonia (NH₃) are passed. So, carbon di oxide (CO₂) and ammonia (NH₃) are compressed and reacted at about 100 – 200 atm and at 170 – 190 ⁰C to form ammonium carbamate (NH₄COONH₂).

CO₂ + 2NH₃ -------> NH₄COONH₂ ΔH⁰ = -37.4 Kcal

In the next step urea is formed by dehydration in a low-pressure stripping operation.

NH₄COONH₂ -------> NH₂CONH₂ + H₂O ΔH⁰ = 6.3 Kcal

Process modifications occurs in recycle of unreacted ammonia (NH₃). Undesirable side reaction is---

2NH₂CONH₂ -------> NH₂CONHCONH₂.H₂O

Effect of Temperature

According to Le-chatelier principle an increase in temperature favoured the overall reaction because the rate determining step is endothermic. It has been observed that, at 170 ⁰C, the reaction rate reaches the maximum limit and the reaction rate falls below this temperature.

Effect of Pressure

Increase of pressure has a favourable effect on the yield of urea, so the reaction occurs at high pressure such as 100 – 200 atm.

[Ammonia/Carbon di oxide] Ratio

Used of ammonia in slight excess (at about 10% excess) shift the equilibrium to the product side, so more and more urea is produced.

Phase of Reactant

Carbon di oxide (CO₂) and ammonia (NH₃) are present in liquid state.

Percentage of Conversion

At about 40% urea is produced from ammonium carbamate in this reaction.

Types of the Manufacturing Process

There are three major manufacturing process for the manufactured of urea depending upon the utilization of unreacted ammonia (NH₃) and carbon di oxide (CO₂).

Method – 1

By passing liquid carbon di oxide (CO₂) and liquid ammonia (NH₃) through a silver lined special autoclave in 1:2 molar ratio, ammonium carbamate is formed. Then ammonium carbamate is heated at about 130 – 140 ⁰C and under about 35 atm pressure urea is formed. By this method yield of urea is 40%.

Method – 2

At 160 – 180 ⁰C and at 150 – 200 atm pressure urea can be manufactured by reacting of one part of solid carbon di oxide (CO₂) by weight and two or more parts of ammonia (NH₃) by weight. By this method yield of urea is 65 – 70%.

Method – 3

By this method urea can be manufactured by reacting 3 – 5 moles of liquid ammonia (NH₃) with liquid carbon di oxide (CO₂) at about 400 atm pressure and at about 200 – 210 ⁰C. By this method yield of urea is 75%.

Uses of Urea

Since urea contain about 45 – 47 % of nitrogen, so urea widely used as most important nitrogenous fertilizer. The P^H of the soil does not change by urea, so urea widely used as fertilizer for all types of crops in all kind of soil.

Urea should be applied in combination with earth or sand because urea is highly concentrated.

When the soil contains free water, urea should not be applied.

Diborane Structure and Bonding

2022-12-23T20:59:00.000+05:30

Structure and Bonding of Diborane (B₂H₆)

Boron is an electron deficient element. Due to its electron deficient character, the trivalent boron leads to dimerization to form diborane (B₂H₆). If we assumed that, the structure of diborane (B₂H₆) is similar to single bond structure of ethane (C₂H₆), then this assumption is rejected because single bond structure of ethane (C₂H₆) contains 14 electrons [(4+4 = 8 electrons from two carbon atoms) and (1x6 = 6 electrons from six hydrogen atoms)] but in diborane there are only 12 electrons [(3+3 = 6 electrons from two boron atoms) and (1x6 = 6 electrons from six hydrogen atoms)].

If we further assumed that, diborane (B₂H₆) molecule contains two one-electron bonds in its structure, to account for 12 electrons then diborane (B₂H₆) must be paramagnetic but actual fact that, the diborane (B₂H₆) molecule is diamagnetic. So, this assumption is also rejected.

Again, if we further assumed that, the diborane (B₂H₆) molecule contain two-electron three-centred bond (2e-3c bond), then the problem has been solved.

Electron diffraction study and other physical studies indicate the below structure for the molecule of diborane (B₂H₆).

Two B―H―B bridges joined the two B atoms. The B―H bridge bond length (1.33 A⁰) are longer than B―H terminal bond length (1.19 A⁰). The B―B distance is 1.77 A⁰. Specific heat measurement data confirm that the two bridging H-atoms are in a plane perpendicular to the rest of the molecule and prevent rotation between the two B-atoms.

Raman spectroscopy confirm that four terminal H-atoms are in a different environment from two bridging H-atoms. It is also confirmed by the fact that, methylation of diborane (B₂H₆) with B(CH₃)₃ produced tetramethyl diborane [(CH₃)₄B₂H₂], further attempt for methylation breaking the molecule into B(CH₃)₃ fragments. Four terminal H-atoms which are linked to B-atoms by normal covalent bonds, means two-electron two-centred bond (2e-2c) are replaced on methylation. The two bridging H-atoms, which are not methylated are connected through peculiar two-electron three-centred (2e-3c) bonds. The whole structure of diborane (B₂H₆) molecule can be explained as follows.

Electron configuration of boron is----

1s² 2s² 2p³

So, boron contains three electrons in its outermost shell. Two boron atoms of diborane (B₂H₆) molecule undergoes sp³ hybridisation. Two sp³ hybrid orbitals of each boron atoms overlap with the 1s orbitals of two terminal H-atoms.

The other two sp³ hybrid orbitals of one B atom overlap with two other sp³ hybrid orbitals of another B atom through the 1s orbitals of the two bridging H-atoms. As a result of these overlap, there formed total two B―H―B two-electron three-centred (2e-3c) bonds.

Such type of bond or molecular orbital has banana shape, so these bent bonds are called banana bonds.

Molecular orbital approach of diborane (B₂H₆) molecule---

Molecular orbital approach of diborane molecule begin with four roughly sp³ hybrid orbitals of each boron atoms and the 1s atomic orbitals of six hydrogen atoms. Two sp³ hybrid orbitals of each boron overlap with two 1s atomic orbitals of two hydrogen atoms and formed four terminal B―H bonds (covalent bonds, 2e-2c bonds). Due to this overlap four bonding and four anti bonding molecular orbitals are formed by four sp³ hybrid orbitals of two boron (two sp³ hybrid orbitals of each boron) and four 1s atomic orbitals of four hydrogen atoms. The four bonding molecular orbitals are occupied by eight electrons (four electrons from two boron atoms and four electrons from four hydrogen atoms). Remaining four sp³ hybrid orbital of two boron (two sp³ hybrid orbitals from each boron) and two 1s atomic orbitals of remaining two hydrogen atoms forms two sets of B―H―B bridge bonds (2e-3c bonds). Due to this overlap three sets of molecular orbitals are formed. One set of bonding molecular orbitals, one set of nonbonding molecular orbitals and one set of antibonding molecular orbitals. Remaining four electrons (two from two boron atoms and two from two hydrogen atoms) occupied the lowest energy bonding molecular orbitals.

The molecular orbital diagram of diborane (B₂H₆) molecule----

Boron

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BORON

Symbol --- B

Abundance --- 0.00086% in earth’s crust

Allotropes --- α-rhombohedral, β-rhombohedral, β-tetragonal

Physical state --- solid

Colour --- black brown

Discovery --- Gay-Lussac and Thenard (1808)

First isolation --- Humphry Davy

Atomic no --- 5

Atomic weight --- 10.81

Period --- 2

Group --- 13 or IIIA

Block --- p

Known isotopes --- ₅B⁸, ₅B⁹, ₅B¹⁰, ₅B¹¹, ₅B¹², ₅B¹³, ₅B¹⁴, ₅B¹⁵, ₅B¹⁶

Stable isotopes --- ₅B¹⁰, ₅B¹¹

Isotopic abundance --- ₅B¹⁰ (19.7%), ₅B¹¹ (80.3%)

Melting Point --- 2348 K (2075 ⁰C)

Boiling Point --- 4198 K (3925 ⁰C)

Density --- 2.45 g/cm³

Density --- 2.08 g/cm³ (liquid)

Electron configuration --- [He] 2s² 2p¹

Electrons per shell --- 2 (1 st shell), 3 (2 nd shell)

Oxidation state --- +3

Valance --- 3

Electronegativity --- 2.04

Electron affinity --- 26.4 KJ/mol

Ionisation energy --- 800 KJ/mol (1 st), 2426 KJ/mol (2 nd), 3659 KJ/mol (3 rd), 25000 KJ/mol (4 th)

Atomic radius --- 90 pm

Covalent radius --- 84 pm

Van der Waals radius --- 192 pm

Ionic radius (B³⁺) --- 27 pm

E⁰(V) --- -0.89 [B³⁺+3e = B(s)]

Crystal structure --- rhombohedral

Heat of fusion --- 50 KJ/mol

Heat of vaporization --- 507 KJ/mol

ΔH⁰_atomisation--- 565 KJ/mol

Molar heat capacity --- 11.08 J/(mol-K)

Specific heat --- 1030 J/ (Kg K)

Thermal expansion --- 5-7 μm/ (m K)

Thermal conductivity --- 27.4 W/ (m K)

Molar volume --- 4.39 x 10^-6

Speed of sound --- 16200 m/s

Magnetic type --- diamagnetic

Lattice angles --- 1.01334, 1.01334, 1.01334

Lattice constants --- 506 pm, 506 pm, 506 pm

Quantum numbers --- ²P_1/2

Neutron cross section --- 760

Neutron mass absorption --- 2.4

Electrical conductivity --- 0.0001 S/m

Electrical resistivity --- 10⁶ Ωm

Mohs hardness --- 9.5

Bulk modulus --- 320 GPa

Vickers hardness --- 49000 MPa

Nitrolim calcium cyanamide

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NITROLIM or CALCIUM CYANAMIDE

Nitrolim or calcium cyanamide is one of the most important fertilizers in the present day, contain about 20% of nitrogen. The formula of nitrolim or calcium cyanamide is CaNCN or CaCN₂ and it is represented as N≡C―N=Ca or [(Ca²⁺) (^-N=C=N^-)], it is a derivative of cyanamide, N≡C―NH₂. Nitrolim is grey powdered fertilizer.

When limestone means calcium oxide (CaO) and coke (C) heated in an electric furnace at about 2000⁰C, calcium carbide (CaC₂) is formed.

At 2000⁰C, CaO + 3C ------> CaC₂ + CO

When this calcium carbide (CaC₂) treated with nitrogen (N₂), calcium cyanamide or nitrolim is formed, this reaction is highly exothermic.

CaC₂ + N₂ -------> CaNCN + C ΔH = - 72.7 Kcal

Some important considerations during this manufacturing process are---

Temperature: Since the reaction is exothermic, so according to Le-chatelier principle, this reaction is highly favorable at low temperature, but this off set the activation energy of the reaction.

Activator: CaF₂ is used as an activator to overcome the above difficulty. At low temperature, CaF₂ activates the process of the reaction at a reasonably in speed.

Fixation: Nitrogen (N₂) fixation limit cannot pass over 85% limit.

Raw Materials

Raw materials required for the manufactured of nitrolim or calcium cyanamide are calcium carbide (CaC₂) [which is prepared from lime stone or calcium oxide (CaO) and coke (C)] and nitrogen (N₂).

Manufacturing Process

Powdered calcium carbide (CaC₂) along with CaF₂ (activator) are taken in the electric furnace fitted with pipe to get supply of nitrogen (N₂). In the electric furnace, the central carbon electrode is connected to high voltage mains. When the temperature of the electric furnace reaches to 900⁰C, highly exothermic reaction leading to the formation of the calcium cyanamide or nitrolim. Allowing the reaction to continue by its own liberated heat at about 40-60 hours for completion. During this process temperature is maintained at about 1000⁰C. After completion the reaction solid chank are taken out, and then disintegrated, powdered. Now first water is sprayed over the powdered to destroy any residual carbide and then spray oil. The grey powdered thus obtained is suitable for use.

Uses of Nitrolim or Calcium Cyanamide

Nitrolim or calcium cyanamide is used as a fertilizer due to its slow conversion into ammonia (NH₃) and nitrate (NO₃^-). So, it is a good fertilizer as its effects are prolonged nature.

Action of Calcium Cyanamide or Nitrolim as Fertilizer

In the soil, when finely powdered nitrolim is applied, it gets hydrolyzed to calcium hydroxide [Ca(OH)₂] and urea (H₂N―CO―NH₂). This hydrolysis process is catalysed by soil catalysis or microorganisms, which are present in the soil.

CaCN₂ + 4H₂O ------> Ca(OH)₂ + CO(NH₂)₂ + H₂O

Or, CaCN₂ + 3H₂O ------> Ca(OH)₂ + CO(NH₂)₂

The urea formed in this process, is then hydrolysed with the help of enzyme urease into ammonia. The ammonia is then converted to nitrates by oxidation with the help of enzyme of bacteria.

CO(NH₂)₂ + H₂O ------> CO + 2NH₃

2NH₃ + 3O₂ -----> 2NO₂^- . 2H₂O + 2H⁺ + Energy

2NO₂^- + O₂ -------> 2NO₃^- + Energy

Albendazole and Mebendazole

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Synthesis of Albendazole and Mebendazole

Albendazole

Albendazole is a benzimidazole derivative, widely used across the globe for the treatment of neurocysticerosis and echinococcosis and other intestinal nematode infection. Albendazole is found to be quite effective as a single dose treatment for ascariasis. Albendazole is also found in the treatment of infection caused by various worms such as roundworm, whipworm, threadworm and hookworm. A recommended multi dose therapy with albendazole is found to be very effective in the complete eradication of pinworm chlonorchiasis and capillariasis.

Synthesis of Albendazole

Albendazole is prepared by three steps----

Step – 1-----

In this step at first, 3-chloro-6-nitroacetanilide is reacted with propyl mercaptan, as a result 3-propylthio-6-nitroacetanilide is formed. The nitro group present at position 6 in 3-propylthio-6-nitroacetanilide is reduced by hydrogen in presence of palladium on carbon (Pd-C) as a catalyst. As a result, 4-(propylthio)-o-phenylenediamine is formed.

Step – 2-----

In this step, s-methylisothiourea sulfate is reacted with methylchloro formate in presence of NaOH at p^H 8. As a result, methyl-s-methylthiourea carboxylate is formed.

Step – 3------

In the final step, 4-(propylthio)-o-phenylenediamine formed in step–1 and methyl-s-methylthiourea carboxylate formed in step–2, are reacted. As a result, albendazole is formed.

Mebendazole

Mebendazole is also a benzimidazole derivative, widely used across the globe for the treatment of infection caused by hookworm, pinworm, roundworm, whipworm, guinea worm. Mebendazole is used for the treatment of infection caused by Trichuris trichiura, Enterobius vermicularis. Mebendazole is also used as an alternative medicine for Visceral Larva Migrans. Mebendazole is found very effective against nematodes and cestodes.

Synthesis of Mebendazole

Mebendazole is prepared by three steps---

Step – 1-----

In this step at first, 4-chlorobenzophenone reacted with mixed acid (HNO₃+H₂SO₄), as a result 4-chloro-3-nitrobenzophenone is formed. Now 4-chloro-3-nitrobenzophenone reacted with ammonia in presence of methanol at 125⁰C. As a result, 4-amino-3-nitrobenzophenone is produced. The nitro group present at position 3 in 4-amino-3-nitrobenzophenone is reduced by hydrogen in presence of palladium on carbon (Pd-C) as a catalyst. As a result, diaminobenzophenone is formed.

Step – 2-----

In this step, s-methylisothiourea sulfate reacted with methylchloro formate in presence of NaOH at p^H 8. As a result, methyl-s-methylthiourea carboxylate is produced.

Step – 3-----

In the final step, diaminobenzophenone formed in step-1 and methyl-s-methylthiourea carboxylate formed in step-2 are reacted. As a result, mebendazole is formed.

Neoprene Rubber

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NEOPRENE RUBBER

Neoprene rubber is a type of synthetic rubber which is made by several chloroprene monomer unit. Over a wide range of temperature neoprene maintains its flexibility and exhibits high chemical stability. In market neoprene rubber available in both form, such as solid form and latex form and used in a variety of application.

In the manufacture of neoprene rubber, the raw materials required are acetylene (C₂H₂) and hydrochloric acid (HCl). Acetylene (C₂H₂) is washed by concentrated sulfuric acid (H₂SO₄) for purification. In presence of cuprous chloride (CuCl) pure acetylene (C₂H₂) dimerised to vinyl acetylene (CH₂=CH―C≡CH). During this process some amount of divinyl acetylene is also produced, which is separate from vinyl acetylene immediately as an immiscible oil, because this divinyl acetylene violently active compound.

If pure acetylene gas rapidly sweeping through a catalyst solution [this catalyst solution contains concentrated solution of CuCl and NH₄Cl at ordinary temperature] then the formation of divinyl acetylene is avoided.

Now the mixture of vinyl acetylene with some amount of divinyl acetylene and some amount of unreacted acetylene is cooled. Due to cooling unreacted acetylene separated as a gas and the mixture of vinyl acetylene and divinyl acetylene are condensed. Now the vinyl acetylene in gas form is passed through a solution of CuCl and concentrated hydrochloric acid (HCl) at 30⁰C. As a result, chloroprene is formed which is the monomeric unit of neoprene rubber.

Now this chloroprene vapour which contain some amount of HCl gas is allowed to cool. As a result, chloroprene condenses to liquid form from vapour form and HCl gas separated which is reused. At ordinary temperature the emulsion polymerization of chloroprene gives neoprene. This emulsion polymerization process is very rapid and this polymerization process follows free radical mechanism pathway.

To increase the plasticity and stabilization of the polymer, tetraethyl thiuram disulphide is added after the polymerization process.

Neoprene can be vulcanized by the following ways----

By heating alone.

By used of ZnO and MgO as a vulcanizing agent.

By used of antimony sulphide.

Properties of Neoprene rubber

Chemically neoprene rubber very closely related to natural rubber, neoprene rubber has higher elongation percentage than natural rubber but tensile strength of neoprene rubber is lower than natural rubber. Neoprene rubber is soluble in polar solvent and it has good weathering resistance. Neoprene rubber is not attacked by alkali below 50% strength and it is resistance to vegetable and mineral oils and also resistance to oxidising agents such as oxygen and ozone and in high temperature.

Application of Neoprene rubber

Neoprene rubber has various uses such as, for making gaskets in oil refining plants, for making various standard engineering material, in conveyor belts, for printing rollers and for making rubber cements.

ELEMENTAL CHEMISTRY

Ultramarine Blue

ULTRAMARINE BLUE

Preparation of Blue Ultramarine

Uses of Ultramarine

Limitation

Electron Affinity

ELECTRON AFFINITY

Periodic Trend of Electron Affinity

(1) Variation Along a Period

(2) Variation Along a Group

Factors Affecting the Magnitude of Electron Affinity

(1) Size of the Atom

(2) Nuclear Charge

(3) Electron Configuration

Electron Affinity of Some Cases

(1) The electron affinity values of the noble gases are negative---

(2) Halogens possess large positive electron affinity values---

(3) Electron affinity values of Beryllium (Be) Magnesium (Mg) and Nitrogen (N) are negative---

(4) The 2 nd electron affinity value of oxygen (O) and sulfur (S) are negative---

Magnesium

MAGNESIUM

Oils Fats and Waxes

OILS FATS AND WAXES

Classification of Oils and Fats

Difference Between Fats and Oils

Difference Between Vegetable and Mineral Oils

Examples of Animal Oils

Examples of Vegetable Oils

Examples of Mineral Oils

Sodium

SODIUM

Preparation of Alkanes

PREPARATION OF ALKANES

(1) From Unsaturated Hydrocarbons

(2) From Alkyl Halides

(A) Through Grignard Reagent

(B) By Wurtz Reaction

(C) By Corey-House Synthesis

(D) Reduction of Alkyl Halides

(3) From Carbonyl Compounds

(A) By Clemmensen Reduction

(B) By Wolff-Kishner Reduction

(4) From Carboxylic Acid

(A) By Decarboxylation Process

(B) Kolbe’s Electrolytic Method

(5) From Alkyl Borane

(6) From Alcohol

Neon

NEON

Electronegativity

ELECTRONEGATIVITY

Scales of Electronegativity

Pauling’s Scale of Electronegativity

Mulliken’s Approach

Allred and Rochow’s Scale of Electronegativity

Periodic Variation of Electronegativity

Factors Affecting the Magnitude of Electronegativity

(1) Size of the atom---

(2) Oxidation state---

(3) Formal charge of an atom---

(4) Nature of hybridisation---

(a) Compare the acidity of methane (CH4), ethylene (C2H4) and acetylene (C2H2)---

(b) Compare the basicities of R―NH2, C5H5N and R―C≡N ---

(5) Nature of other atoms---

(6) Ionisation energy and Electron affinity---

Fertilizer

FERTILIZER

Type of Fertilizer

(1) Complete fertilizer---

(2) Incomplete fertilizer---

(3) Direct fertilizer---

(4) Indirect fertilizer---

(5) Micro fertilizer---

(6) Mixed fertilizer---

Essential Requirement of a Fertilizer

Nitrogenous Fertilizer

Phosphatic or Phosphorus Fertilizers

Potassium Fertilizer

Fluorine

(a) Compare the acidity of methane (CH₄), ethylene (C₂H₄) and acetylene (C₂H₂)---

(b) Compare the basicities of R―NH₂, C₅H₅N and R―C≡N ---

(1) Borax from boric acid (H₃BO₃) ---

(2) Borax from colemanite (2CaO, 3B₂O₃) ---