SOLUTION

1.Explain why on addition of 1 mol glucose to 1 litre water the boiling point of water increases.
2.(a)Write two differences between ideal solutions and non-ideal solutions.
(b) Blood cells are isotonic with 0.9% sodium chloride solution. What happens if we place blood
cells in a solution containing
(i) 1.2% sodium chloride solution? (ii) 0.4% sodium chloride solution?
3.(i) Out of 1 M glucose and 2 M glucose, which one has a higher boiling point and why?
(ii) What happens when the external pressure applied becomes more than the osmotic pressure of
solution?
4. What is van’t Hoff factor? What types of values can it have if in forming the solution, the solute
molecules undergo (i) Dissociation? (ii) Association?
5.What type of deviation is shown by a mixture of ethanol and acetone? Give reason.
6.State Henry’s law about dissolution of a gas in a liquid and mention two of its important
applications.
7.What is meant by +ve and -ve deviations from Raoult’s law and how is the sign of ∆H solution
related to +ve and -ve deviations from Raoult’s law?
8.State Raoult’s law for a solution containing volatile components. How does Raoult’s law become a
special case of Henry’s law?
9. Differentiate between molarity and molality in a solution. What is the effect of temperature
change on molarity and molality in a solution?
10. Define osmosis and osmotic pressure. How is osmotic pressure related to the concentration of
a solute in a solution? Why osmotic pressure is a colligative property?
11.(a)Gas (A) is more soluble in water than Gas (B) at the same temperature. Which one of the two
gases will have the higher value of KH (Henry’s constant) and why?
(b)In non-ideal solution, what type of deviation shows the formation of maximum boiling
azeotropes?
12.(a)On mixing liquid X and liquid Y, volume of the resulting solution decreases. What type of
deviation from Raoult’s law is shown by the resulting solution? What change in temperature would
you observe after mixing liquids X and Y?
(b)What happens when we place the blood cell in water (hypotonic solution)? Give reason.
13.Define azeotropes. What type of azeotrope is formed by positive deviation from Raoult’s law?
Given an example.
14.How is the vapour pressure of a solvent affected when a non-volatile solute is dissolved in it?
15.What is the similarity between Raoult’s law and Henry’s law?
16.What is the effect of temperature on the solubility of a gas in a liquid?
17.An aqueous solution of sodium chloride freezes below 273 K. Explain the lowering in freezing
points of water with the help of a suitable diagram.
18.Why do gases nearly always tend to be less soluble in liquids as the temperature is raised?
19.Explain why aquatic species are more comfortable in cold water rather than in warm water.
20.What is the advantage of using osmotic pressure as compared to other colligative properties for
the determination of molar masses of solutes in solutions?
21.Non-ideal solutions exhibit either positive or negative deviations from Raoult’s law. What are
these deviations and why are they caused? Explain with one example for each type.
22.What type of intermolecular attractive interaction exists in the pair of methanol and acetone?
23.On mixing liquid X and liquid Y, the volume of the resulting solution increases. What type of
deviation from Raoult’s law is shown by the resulting solution? What change in temperature would
you observe after mixing liquids X and Y?
24.How can the direction of osmosis be reversed? Write one use of reverse osmosis.
25.What do you understand by depression of freezing point?
26.Why does a solution containing non-volatile solute have higher boiling point than the pure
solvent? Why is elevation of boiling point a colligative property?
27.Name the solution which follows Raoult’s law at all concentrations and temperatures.
28.Measurement of which colligative property is preferred for determination of molar mass of
biomolecules?
29.Out of two 0.1 molal solutions of glucose and of potassium chloride, which one will have a higher
boiling point and why?
30.(i) Why is an increase in temperature observed on mixing chloroform and acetone?
(ii) Why does sodium chloride solution freeze at a lower temperature than water?
31.Define the following terms :
(a) Isotonic solutions (b) Hypertonic solutions(c)Hypotonic solution (d) Boiling poin(e)Freezing point
(f)Vapour pressure (g) Ppm (h) Cryoscopic constant molal depression constant or freezing point
depression constant (i) Abnormal molar mass (j) Mole fraction (k) Molal elevation constant (Kb) or
Boiling point elevation constant for a solvent or ebullioscopic constant
(l) Ideal solution (m) Mole fraction (n) Colligative properties

Answer 1: Glucose is a non-volatile solute, therefore boiling point of water increases due to
lowering of vapour pressure.
Answer2:(i)Exosmosis will occur which results in shrinkage of RBCs.
(ii)Endosmosis will occur and blood cell will swell.
Answer 3 :(i) 2M glucose because it has more number of particles
(ii) Reverse osmosis will occur ,the solvent will flow from the solution into the pure solvent through
the semi-permeable membrane.
Answer 4: Van’t Hoff factor (i) : It is defined as the ratio of the experimental value of the colligative
property to the calculated value of the colligative property .
In dissociation i > 1. In association i < 1
Answer 5 : positive deviation because intermolecular interactions are weak in solution.
Answer 11 :(a)Gas (B) will have higher value of KH because lesser the solubility of a gas in a given
solvent, higher will be the value of KH for a gas. (ii) Negative deviations from Raoult’s law
Answer 12 : (a) It shows negative deviations from Raoult’s law. There will be rise in temperature.
(∆Hmix < 0) (b)Blood cell will swell due to endosmosis as water enters the cell.
Answer 13: Azeotropes : Liquid mixture which distills without change in compositions are called
azeotropic mixtures or Azeotropes(constant boiling mixtures ).
In positive deviations from Raoult’s law, minimum boiling point azeotropic mixture is formed. For
example, 95% ethanol + 5% water.
Answer 15: Similarity between Raoult’s law and Henry’s law is that the partial pressure or vapour
pressure of the volatile component (gas) is directly proportional to the mole fraction of that
component in the solution.
Answer 16: Solubility of gas decreases with increase of temperature at the same pressure.
Answer 17: An aqueous solution of sodium chloride freezes below 273 K because vapour pressure
g of the solution is g less than that of the pure solvent.
Answer 18: This is because the dissolution of gas in liquid is an exothermic process. The solubility
should decrease with increase in temperature.
Answer 19: As solubility of gases decreases with increase of temperature, less oxygen is available
in summer in the lake. Hence the aquatic species feel more comfortable in winter (low temperature)
when the solubility of oxygen is higher.
Answer22: Solute-solvent dipolar interactions exist in the pair of methanol and acetone.
Answer29: 0.1 molal KC1 solution will have higher boiling point, because the number of particles
are double
Answer 30: (i) It is because force of attraction between chloroform and acetone is more than the
force of attraction between chloroform-chloroform or Acetone-Acetone. Therefore, ∆H = -ve, i.e.
exothermic process, therefore, there is increase in temperature.
(ii) It is because when NaCl is added, vapour pressure of solution becomes less and. freezing point
is lowered.