Class 12 Chapter Solution Test Paper

**Chemistry Class 12 Chapter Solution Test Paper – 2**

Class 12 Chapter Solution Test Paper

**Que 1.** A 10% solution of urea is isotonic with a 20% solution of ‘x’ at the same temperature. Calculate the molecular weight of x.

**Que 2.** In the determination of the molar mass of A + B – using a colligative property, what may be the value of van’t Hoff factor if the solute is 50% dissociated?

**Que 3.** The density of water in a lake is 1.25 g mL^{–1} and one kg of this water contains 92g of Na^{+} ions. What is the molarity and molality of Na^{+} ions in the water of the lake? (Atomic mass of Na = 23.00 u)

**Que 4.** If N_{2} gas is bubbled through water at 293 K, how many millimoles of N_{2} gas would dissolve in 1 litre of water? Assume that N_{2} exerts a partial pressure of 0.987 bar. Given that Henry’s law constant for N_{2} at 293 K is 76.48 kbar.

**Que 5.** A solution is prepared by dissolving 10 g of non-volatile solute in 200 g of water. It has a vapour pressure of 31.84 mm Hg at 308 K. Calculate the molar mass of the solute. (Vapour pressure of pure water at 308 K = 32mmHg)

**Que 6.** The vapour pressure of pure benzene at a certain temperature is 0.85 bar. A non-volatile, non-electrolyte solid weighing 0.5 g is added to 39.0 g of benzene (molar mass 78 g mol^{–1}). The Vapour pressure of the solution, then, is 0.845 bar. What is the molar mass of the solid substance?

**Que 7.** Derive an expression for Raoult’s law when the solute is non-volatile

**Que 8.** 18 g of glucose, C_{6}H_{12}O_{6}, is dissolved in 1 kg of water in a saucepan. At what temperature will water boil at 1.103 bar? (K_{b} for H_{2}O is 0.52 k kg mol^{–1})

**Que 9.** Find the boiling point of a solution containing 0.520 g of glucose (C_{6}H_{12}O_{6}) dissolved in 80.2 g of water. [Given: K_{b} for water = 0.52 K/m]

**Que 10.** The boiling point of benzene is 353.23 K. When 1.80 g of non-volatile solute was dissolved in 90 g of benzene, the boiling point is raised to 354.11 K Calculate the molar mass of solute. K_{b} for benzene is 2.53 K kg mol^{–1}.

**Que 11.** 1.0 g of a non-electrolyte solute dissolved in 50.0g of benzene lowered the freezing point of benzene by 0.40K. The freezing point depression constant of benzene is 5.12K kg mol^{–1}. Find the molar mass of the solute.

**Que 12.** 200 cm3 of an aqueous solution of protein contains 1.26 g of the protein. The osmotic pressure of such a solution at 300 K is found to be 2.57 × 10^{–3} bar. Calculate the molar mass of the protein.

**Que 13.** A 1.00 molal aqueous solution of trichloroacetic acid (CCl_{3}COOH) is heated to its boiling point. The solution has a boiling point of 100.18 °C. Determine the van’t Hoff factor for trichloroacetic acid. (K_{b} for water = 0.512 K kg mol^{–1}).

**Que 14.** A 0.561m solution of an unknown electrolyte depresses the freezing point of water by 2.93 °C. What is van’t Hoff factor for this electrolyte? The freezing point depression constant (K_{f}) for water is 1.86 °C kg mol^{–1}.

**Que 15.** An electrolyte AB is 50% ionised in an aqueous solution. Calculate the freezing point of 1 molal aqueous solution.

Class 12 Chapter Solution Test Paper

**Que 16.** Calculate the boiling point of 1 molar solution of solute (Molar mass 74.5 g mol^{–1}). The density of the solution is 1.04 g mL^{–1} and K_{b} for water is 0.52 K kg mol^{–1}.

**Que 17.** Calculate the amount of sodium chloride which must be added to one kilogram of water so that the freezing point of water is depressed by 3 K. [Given: K_{f} = 1.86 K kg mol^{–1}, Atomic mass: Na = 23.0, Cl = 35.5].

**Que 18.** 0.6 mL of acetic acid (CH_{3}COOH), having a density of 1.06 g mL^{–1}, is dissolved in 1 litre of water. The depression in freezing point observed for this strength of acid was 0.0205 °C. Calculate the van’t Hoff factor and the dissociation constant of acid.

**Que 19.** Calculate the amount of CaCl_{2} (molar mass 111 g mol^{–1}) which must be added to 500 g of water to lower the freezing point by 2K, assuming CaCl_{2} is completely dissociated. (K_{f} = 1.86 K kg mol^{–1}).

**Que 20.** 6.90 M solution of KOH in water contains 30% by mass of KOH. Calculate density and molality of KOH solution. [K = 39, O = 16, H = 1].

**Que 21.** Why do doctors advise gargling with saline water in case of a sore throat?

**Que 22.** Explain why a solution of chloroform and acetone shows negative deviation from Raoult’s law?

**Que 23.** Discuss the biological and industrial importance of osmosis.

**Que 24.** A binary solution contains two liquid components A and B having the same mol fractions. Will their mole fraction in the vapour phase be the same or different?

**Que 25.** (a) What are non-ideal solutions?

(b) What role does the molecular interaction play in deciding the vapour pressure of solutions

(i) alcohol and acetone

(ii) chloroform and acetone?

**Que 26.** What is meant by the abnormal molecular mass of solute? Discuss the factors which bring abnormality in the experimentally determined molecular masses of solutes using colligative properties.

**Que 27.** What is van’t Hoff factor? How does it modify the equation for elevation in boiling point?

**Que 28.** Define the term osmotic pressure. Describe how the molecular mass of a substance can be determined by a method based on the measurement of osmotic pressure?

**Que 29.** What are the advantages of using osmotic pressure as compared to other colligative properties for the determination of molar masses of solutes in solutions?

**Que 30.** (i) Define cryoscopic constant.

(ii) Define ebullioscopic constant.

Class 12 Chapter Solution Test Paper

**Chapter Solutions Test Paper – 1**