Class 12 Chemistry Solutions

1. SOLUTIONS
RANIYA ABDU
ARC

2. When two or more substances mix and form a uniform or homogeneous
mixture then such a mixture.
• Solute: A substance that is dissolved in another substance in lesser amount, forming a
solution.
For example: Sugar, salt, etc.
• Solvent: A substance in which another substance is dissolved in larger amount forming a
solution.
For example: Water, milk, etc
If the constituents of the solution are two, it is called binary, if three then
ternary, if four then quaternary and so on.

3. TYPES OF SOLUTIONS
Any state of matter (solid, liquid or gas) can act both as a solvent and as a solute during the
of a solution. Therefore, depending upon the physical states of solute and solvent, we can have
following nine different types of solutions
Amount of solute dissolved in unit volume of solution or unit mass of solvent is
called concentration.

4. • Aqueous Solutions & Non – aqueous Solutions
• Saturated & Unsaturated Solutions
• Solubility : Solubility can be defined as the maximum amount of solute that can be dissolved in 100 g
of solvent to form a saturated solution at a given temperature.
• Causes of Solubility:
• (i) Inter ionic attraction in the solute molecules: Molecules are stabilised in the lattice due to
electrostatic forces and the energy released is known as lattice energy.
• (ii) Inter molecular attraction between solvent molecules.
• (iii) Solvation: It denotes the force of attraction between solute and solvent molecules.
• (iv) Temperature
• Factors affecting Solubility:
• (i) Nature of Solute and Solvent: “Like dissolves like” i.e., polar solvents like water and ammonia can
dissolve polar solute or ionic solute while non-polar solvents can dissolve non-polar organic solutes.

5. • (ii) Temperature: Solubility increases with increase in temperature. It increases for endothermic reaction
while it decreases for exothermic reaction.
• (iii) Pressure: The solubility of solid in liquid is not affected significantly by pressure because solids and
liquids cannot be compressed.
• (iv) Hydration Energy: It is the amount of energy released when ions formed by 1 mole of ion get
hydrated. It is an exothermic process

7.  Mass percentage :
It is the amount of solute in grams dissolved per 100 gm of solution
 Volume percentage:
It is defined as volume of a solute dissolved per 100 ml of solution

8.  Mass by volume percentage
It is defined as mass of solute dissolved per 100 ml of solution.
 Parts per million (ppm)
It can be defined as the parts of a component per million parts of the solution.
It is used to express the concentration of a solute present in trace quantities.

9.  Molality (m)
It is defined as the number of moles of solute per 1000 g or 1 kg of solvent

10.  Molarity (M)
It is defined as the number of moles of solute per litre of solution
 Normality (N)
It is defined as number of gram equivalents of solute dissolved per litre of solution

11. Molarity and Normality of a mixture of solution produced by mixing two solutions having same solvent
 Mole Fraction (X)
Ratio of number of moles of one component in the solution to the total number of moles of all components in the
solution is called mole fraction

12. “If a system under equilibrium is subjected to a change in temperature, pressure, or concentration,
then the equilibrium shifts itself in such a way to undo or neutralise the effect of change.”
Le Chatelier’s Principle
• Exothermic reactions are favoured by low temperature
• Endothermic reactions are favoured by high temperature
• On the altering temperature, if the forward reaction is exothermic, the
backward reaction will be endothermic and vice versa.
• the increase in temperature shifts the equilibrium in the direction of the
endothermic reaction
• decrease in temperature shifts the equilibrium in the direction of an exothermic
reaction.

13. Eg:The formation of ammonia is an exothermic process, while the reverse
is an endothermic process.
Eg: The formation of nitric oxide by the reaction of nitrogen and oxygen is an
endothermic reaction.
 The effect of pressure depends upon the number of moles of the reactants and the product
involved in a particular reaction.
Increasing pressure shifts the equilibrium in the direction of a decrease in the gaseous moles.

14. Henry’s Law
It states “at a constant temperature the solubility of gas in a liquid is directly proportional to the
pressure of gas”. In other words, “the partial pressure of gas in vapour phase is proportional to the mole
fraction of the gas in the solution”
P = KH x
When a non-volatile solute is dissolved in a volatile solvent, the vapour pressure of solution is less
than that of pure solvent.
Raoult’s Law
It states that “for a solution of volatile liquids the partial vapour pressure of each component in the
solution is directly proportional to its mole fraction”.

15. Using Dalton’s law of partial pressure the total pressure of solution is calculated.
 Raoult’s Law becomes a special case of Henry’s Law