Chemistry

CHAPTER 3-CLASSIFICATION

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v MODERN PERIODIC LAW

Physical and chemical properties of an element are the periodic function of the atomic number.

v FACTORS AFFECTING ATOMIC SIZE

· The attraction of electron.

I.e. atomic size α 1/nuclear charge

· Number of shells

Number of shells α atomic size.

· Screening effect

The decrease in the force of attraction exerted by the nucleus on the valence electron due to the presence of inner electron

Screening effect α atomic size

v IONISATION ENTHALPY (IE)

The minimum amount of energy required to remove the most loosely bound electron from a isolated gaseous atom.

v ELECTRON AFFINITY (ELECTRON GAIN ENTHAPLY)

The amount of energy released when an electron is added to an isolated gaseous atom.

v ELECTRONEGATIVITY

The tendency of an element to attract an electron to it.

v ELECTRONIC CONFIGURATION

Refer NCERT text.

CHAPTER 3-CLASSIFICATION

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v MODERN PERIODIC LAW

Physical and chemical properties of an element are the periodic function of the atomic number.

v FACTORS AFFECTING ATOMIC SIZE

· The attraction of electron.

I.e. atomic size α 1/nuclear charge

· Number of shells

Number of shells α atomic size.

· Screening effect

The decrease in the force of attraction exerted by the nucleus on the valence electron due to the presence of inner electron

Screening effect α atomic size

v IONISATION ENTHALPY (IE)

The minimum amount of energy required to remove the most loosely bound electron from a isolated gaseous atom.

v ELECTRON AFFINITY (ELECTRON GAIN ENTHAPLY)

The amount of energy released when an electron is added to an isolated gaseous atom.

v ELECTRONEGATIVITY

The tendency of an element to attract an electron to it.

v ELECTRONIC CONFIGURATION

Refer NCERT text.

CHAPTER 2-STRUTURE OF ATOMS

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v RUTHERFORD NUCLEAR MODEL OF ATOM –features

· The entire mass and the positive charge are concentrated at the centre known as nucleus.

· The negatively charged electron which encircle the nucleus.

· Most of the space is empty.

Ø FAILURE OF RUTHERFORD MODEL

· By circling around the nucleus it continuously loss energy and fall to nucleus and there will be no atom.

· Inability to explain atomic spectra of elements.

v PHOTOELECTRIC EFFECT

· The phenomenon of ejection of electron from the surface of metals like potassium and caesium, when the frequency (suitable) strikes on it.

Ø LAW OF PHOTOELECTRIC EFFECT

· Only radiation of certain minimum frequency causes this effect. This frequency is called threshold frequency.

· When the radiation of energy hɤ falls on the metal part is used to provide work function (threshold energy) and remaining to impart kinetic energy(K.E).

· Number of electron ejected is proportional to the intensity of radiation.

· K.E α frequency

v BOHR’S MODEL OF ATOM

· An atom consists of a small, heavy negatively charged nucleus in the centre and the electron revolves around it in circular orbits.

· Out of a large number of circular orbits theoretical possible, the electron revolves only in those orbits which here a fixed value of the energy.

· The electron in an atom can have only certain definite values of energy.

· Only that circular path is permissible which satisfy the quantum condition .

· As long as an electron is revolving in a circular path it does not emit or absorb energy.

· When an electron jumps from lower energy to higher energy, energy is absorbed and vice versa.

Ø LIMITATIONS OF BOHR MODEL

· Inability to explain line spectra of multi electron atoms.

· Inability to explain splitting of lines in a magnetic field (Zeeman effect) and in a electric field (Stark effect).

· Inability to explain de Broglie matter wave concept of electron.

· It contradicts with Heisenberg’s uncertainty principle,

v HEISENBERG’S UNCERTAINTY PRINCIPLE

It states that it is impossible to determine exactly both position and momentum of moving microscopic particle simultaneously.

v DUAL NATURE OF ELECTRON

Ø DE BROGILE CONCEPT

· Every matter exhibits both wave and particle nature. From Planck’s relation.

v QUANTUM NUMBERS

Set of four numbers with the help of which we can get complete information about all electrons in an atom.

Ø PRINCIPLE QN (n)

Average distance and energy. n can be 1,2,3 or k,l,m,n etc.

Ø AZIMUTHAL QN (l)

It represents sub shell.

It can have the values 0 to (n-1) value.

Representation—s,p,d…….

Ø MAGNETIC QN (m)

Orientation of electron cloud .

Can have values (2l+1) .

Ø SPIN QN (s)

Represents revolution

v SHAPES OF ORBITALS

v RULES

Ø PAULI’S EXCLUSION

No two electrons can have the same value for all 4 quantum number.

Ø AUFBAU

Electrons are filled in the orbital in the increasing order of energies ,[(n+l)] value.

Ø HUND’S RULE

Paring take place only after all the orbitals are singly occupied.

CONTINUE-CHAPTER 2-SOLUTION

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SOLUBILITY

The solubility of a substance at given temperature is defined as the amount of solid that dissolves in 100g of the solvent to form a saturated solution.

SOLUBILITY OF SOLID IN LIQUID

1. The nature of solute and the solvent. This is in accordance with the basic rule ‘like dissolves like’.

This means ionic or polar compounds dissolve readily in polar solvents and are less or almost insoluble in non polar solvents

2. EFFECT OF TEMPERATURE

If the solute dissolves with absorption of heat (endothermic) the solubility increases with rise in temperature. If the solute dissolves with the evolution of heat (exothermic) the solubility decreases with increase in temperature.

3. EFFECT OF PRESSURE

On the solubility of solid in liquid is generally insignificant because solids and liquids are highly incompressible.

SOLUBILITY OF GAS IN LIQUID

1. Depends upon the nature of the gas and the nature of gas and nature of the liquid.

2. Generally the gases which can be easily liquefied are more soluble in common solvents.

3. The gases which are capable of forming ions in aqueous solution are much more soluble in water than in any other solvent.

4. EFFECT OF TEMPERATURE

The solubility of the gas in liquid decrease with rise in temperature.

5. EFFECT OF PRESSURE

The solubility of gas in liquid is governed by Henry’s law.

Higher the value of K_H at a given pressure the lower is the solubility.

HENRY’S LAW

It states that the partial pressure in vapour phase (P) is proportional to the mole fraction of the gas(X) in the solution and is expressed as P= K_HX , Where K_His the Henry’s Law constant.

Different gases have different K_Hvalues at same temperature.

It can also be defined as the mass of a gas dissolved per unit volume of the solvent at a given temperature is proportional to pressure of the gas in equilibrium with the solution.

APPLICATION OF HENRY’S LAW

REFER NCERT TEXT

SOLID SOLUTION

The solid solution are obtained by dissolving solid solute into solid solvent there are two types of solid solution.

SUBSTITUTIONAL SOLID SOLUTION

It is formed when particles of one substance in its crystal lattice.

Eg: brass, bronze etc

INTERSTITIAL SOLID SOLUTION

It is formed when atoms of one substance occupy the voids in the crystal lattice of host substance.

Eg: tungsten carbide

VAPOUR PRESSURE OF LIGUID SOLUTION

The pressure exerted by the vapour above the liquid surface in equilibrium with the liquid at a given temperature is called vapour pressure.

RAOULTS LAW

It can be explained in two ways

1. It states that at a given temperature, for a solution of volatile liquid the partial pressure of each component in the solution is directly proportional to the mole fraction of that compound.

2. It states that the vapour pressure of the solution is directly proportion to the mole fraction .

CHAPTER 2-SOLUTION

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SOLUTION

A solution is a homogeneous mixture of two or more substance whose composition can be varied within certain limits.

SOLVENT AND SOLUTE

A component which is present in the largest quantity in a solution is called a solvent and the component which is present in the lesser quantity is known as solute

TYPES OF SOLUTION

Depending on the physical state of solute and solvent solution can be classified into 9 types

TYPES OF SOLUTION	SOLUTE	SOLVENT	EXAMPLE
Gaseous	Gas	Gas	O_2(g)+N_2(g)
	Liquid	Gas	CHCl₃ + N_2(g)
	Solid	Gas	Camphor + N_2(g)
Liquid	Gas	Liquid	O_2(g)+ H₂o_(l)
	Liquid	Liquid	Ethanol+ H₂o_(l)
	Solid	Liquid	Glucose + H₂o_(l)
Solid	Gas	Solid	H_(aq)+palladium
	Liquid	Solid	Amalgam +mercury
	Solid	Solid	Copper + gold

EXPRESSNG THE CONCENTRATION

MASS % (w/w)

It is the mass of the component in 100g of the solution.

VOLUME % (v/v)

It is represented as the volume of component per 100 parts of solution by volume.

MASS BY VOLUME % (w/v)

It is the mass of solute dissolved in 100 ml of the solution.

PARTS PER MILLION (ppm)

It is the parts of the component per million parts of the solution.

1 liter of the sea water contains 6 X 10^-3g of dissolved oxygen which is equal to 5.8ppm.

MOLARITY (M)

The no of the mole of the solute dissolved per liter of solution.

Molarity changes with change in temperature because volume changes with change in temperature. This is why molality is preferred rather than molarity for expressing the concentration.

MOLALITY (m)

The no of the moles of the solute dissolved per 1kg of the solvent.

MOLE FRACTION

It is the ratio of number of moles of a component to the total no of moles of all components present in the solution.

CHAPTER 1-BASIC CONCEPTS

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v LAW OF CONSERVATION OF MASS

In all physical and chemical changes, total mass remains same.

v LAW OF CONSTANT PROPORTION

A chemical compound is always found to be made up of same elements combined together in fixed ratio by weight.

v LAW OF MULTIPLE PROPORTION

When two elements combine with each other to form two or more compounds the mass of one of the elements that combine with a fixed weight of other bear a simple whole number ratio to one another.

v GAY LUSSAC’S LAW

When gases react with each other they do so in volumes which bear simple whole number ratio to one another and to the volume of products at STP.

v MOLE CONCEPT

-1 mole=6.022 X 10²³particles=1 GAM=22.4L=1 gram atom

-molecular mass=2 X vapour density

This is very helpful in doing stotiometric problems.

v EMPRICAL FORMULA

It refers to the simplest ratio of the elements of a compound.

Example

Let us find out the empirical formula and molecular formula for the given condition.

Carbon C=75%

Hydrogen H=25%

It is easy to do if you can remember the following table.

Element	percentage	n =%/atomic mass	Ratio of moles of atom	Simplest ratio
carbon	75	75/12=6.25	6.25/6.25=1	1
hydrogen	25	25/1=25	25/6.25=4	4

Therefore the empirical formula is CH₄

Molecular formula=Empirical formula X n

n=molecular mass/empirical formula mass

Here, both MF and EF are same.

v LIMITING REAGENT

The reagent which is present in smaller amount and reacts completely.

v CONCENTRATION

· Mole fraction

· Mass percentage

· Molarity

Number of solute dissolved in 1 liter of solution.

· Molality

Number of solute dissolved per 1 kg of the solvent.

Lets start

2012-05-14T06:20:00.001-07:00

Chemistry

CHAPTER 3-CLASSIFICATION

CHAPTER 3-CLASSIFICATION

CHAPTER 2-STRUTURE OF ATOMS

CONTINUE-CHAPTER 2-SOLUTION

CHAPTER 2-SOLUTION

CHAPTER 1-BASIC CONCEPTS

Lets start

First of all in order to build a strong base we will go through some of the important chapters in 11th standard chemistry.