Chapter 1: Solutions

Important Questions

1. Give one example each of lyophobic sol and lyophilic sol.

2. State Henry’s law correlating the pressure of a gas and its solubility in a solvent and mention two applications for the law.

3. (i) Gas (A) is more soluble in water than Gas
(B) at the same temperature. Which of the two gases will have the higher value of KH (Henry’s constant) and why?
(ii) In non-ideal solution, what type of deviation shows the formation of maximum boiling azeotropes?

4. (a) Differentiate between molality and molarity of a solution. How does a change in temperature influence their values?
(b) Calculate the freezing point of an aqueous solution containing 10.50 g of MgBr2 in 200 g of water. (Molar mass of MgBr2 = 184 g)
( Kf for water = 1.86K kgmol−1 )
OR
(a) Define the terms osmosis and osmotic pressure. Is the osmotic pressure of a solution a colligative property? Explain

(b) Calculate the boiling point of a solution prepared by adding 15.00 g of NaCl to 250.0 g of water. ( Kb for water = 0.512K kgmol−1, Molar mass of NaCl = 58.44 g )

5. (a) State the following:
1. Henry’s law about partial pressure of a gas in a mixture.
2. Raoult’s law in its general form in reference to solutions.
(b) A solution prepared by dissolving 8.95 mg of a gene fragment in 35.0 mL of water has an osmotic pressure of 0.335 torr at 25°C. Assuming the gene fragment is nonelectrolyte, find its molar mass.
OR
(a) Difference between molarity and molality in a solution. What is the effect of temperature change on molarity and molality in a solution?
(b) What would be the molar mass of a compound if 6.21 g of it is dissolved in 24.0g of chloroform to form a solution that has a boiling point of 68.04°C. The boiling point of pure chloroform is 61.7°C and the boiling point elevation constant, for chloroform is 3.63°C/m.

Sample Questions

1. Some liquids on mixing form ‘azeotropes’. What are ‘azeotropes’?

2. State Raoult’s law for the solution containing volatile components. What is the similarity between Raoult’s law and Henry’s law?

3. (a) In reference to Freundlich adsorption isotherm, write the expression for adsorption of gases on solids in the form of an equation.
(b) Write an important characteristic of lyophilic sols.
(c) Based on type of particles of dispersed phase, give one example each of associated colloid and multi molecular colloid.

4. A solution prepared by dissolving 1.25 g of oil of wintergreen (methyl salicylate) in 99.0 g of benzene has a boiling point of 80.31°C and Kb for benzene = 2.53°C kg mol−1

5. Calculate the amount of KCl which must be added to 1kg of water so that the freezing point is depressed by 2K.