Solutions

Question 1

Intensive properties

Answer 1

Properties which do not depend upon the quantity of matter present in the system are called intensive properties

E.g. temperature, density, concentration

Question 2

Extensive properties

Answer 2

Properties which depend upon the quantity of matter present in the system are called extensive properties

E.g. no. of moles, mass, volume, enthalpy

Question 3

Colligative properties

Answer 3

Properties of solutions which depend upon the number of solute particles (molecules or ions) present in a definite amount of solvent but not on the chemical nature of solute are called colligative properties

Question 4

Name 4 colligative properties

Answer 4

1. Lowering of vapour pressure
2. Elevation of boiling point
3. Depression of freezing point
4. Osmotic pressure

Question 5

Henry’s Law

Answer 5

At a constant temperature, solubility of a gas in a liquid is directly proportional to pressure of the gas

Partial pressure of the gas in vapour phase is directly proportional to the mole fraction of the gas in solution (Dalton’s Law)

p= Kₕ ⋅ Χ
where KH= Henry’s Law constant

Question 6

Factors affecting solutbility of a solid in a liquid

Answer 6

1. Nature of solute and solvent: (Non-)polar solutes dissolve readily in (non-)polar solvents but not non-(polar) solvents
2. Temperature:
   * When a substance dissolves with the evolution of heat (exothermic) solubility decreases with rise in temperature
   * When a substance dissolves with absorption of hear (endothermic) solubility increases with rise in termperature

Question 7

Factors affecting V.P. of a liquid

Answer 7

1. Nature of the liquid:
   Weak intermolecular forces- more VP
   Strong intermolecular forces- less VP
2. Temperature
   VP of a liquid increases with increase in temperature
   Addition of non-volatile solute lowers VP

Question 8

GRW addition of non-volatile solute to volatile solvent leads to lowering of VP

Answer 8

1. Pure solvent has only liquid particles on the surface
2. In a solution with non-volatile solite, solid particles also occupy space of the liquid surface
3. Area of surface containing liquids decreases
4. Escaping tendency of molecules decreases
5. VP decreases

Question 9

GRW addition of non-volatile solute to volatile solvent leads to lowering of VP

Answer 9

1. Pure solvent has only liquid particles on the surface
2. In a solution with non-volatile solite, solid particles also occupy space of the liquid surface
3. Area of surface containing liquids decreases
4. Escaping tendency of molecules decreases
5. VP decreases

Question 10

Raoult’s Law: Both statements

Answer 10

1. For a solution of volatile liquids, the partial VP of each component in soln is directly propotional to its mole fraction
   P^o - P / P^o = X_solute
2. For a soln of volatile liquids, the partial VP of each component in the soln at a particular remperature is equal to the product of VP of the component in the pure state and its mole fraction in solution

Pₛₒₗᵤₜᵢₒₙ= Pₛₒₗᵥₑₙₜ ⋅ Χ

Question 11

Ideal solution

Answer 11

A solution of two or more completely miscible liquids that obeys Raoult’s Law at all concentrations and temperatures

Question 12

Non-ideal solutions

Answer 12

Solutions which do not follow Raoult’s Law

Question 13

Positively deviated non-ideal solution

Answer 13

Theoretical VP < Observed VP

E.g.
Water + methanol
Water + ethanol
Acetone + benzene

Question 14

Negatively deviated non-ideal solution

Answer 14

Theoretical VP > Observed VP

E.g.
HCl + water
Chloroform + benzene
Water + nitric acid

Question 15

Azeotropic mixture

Answer 15

The solution of completely miscible liquids, which boils at a constant temperature like a pure liquid and distils over without any change in composition is called an azeotropic mixture

Question 16

minimum BP azeotropic mixture

Answer 16

positively deviated non-ideal soln

Question 17

maximum BP non ideal soln

Answer 17

negatively deviated non-ideal soln

Question 18

Elevation of boiling point

Answer 18

Increase in boiling point of a solvent on addition of a solute to it

Question 19

Molal elevation constant

Answer 19

Elevation in boiling point when molality of a solution is unity

Question 20

Depression of freezing point

Answer 20

Decrease in freezing point of a solvent caused by addition of non-volatile solute

Question 21

Molal depression constant

Answer 21

The depression of freezing point when molality of the soln is unity

Question 22

Osmosis

Answer 22

The spontaneous flow of solvent through a semi-permeable membrane from a pure solvent to solution or from dilute soln to conc soln is called osmosis

more solvent to less solvent

Question 23

Osmotic pressure

Answer 23

External pressure applied to stop the phenomenon of osmosis i.e. the flow of solvent into a soln when the two are separated by a semi-permeable membrane

Question 24

Reverse osmosis

Answer 24

When the pressure applied on the solution is greater than the osmotic pressure of the solution, the solvent starts flowing from soln to solvent through a semi-permeable membrane