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 N2 gas is bubbled through water at 293 K, how many millimoles of N2 gas would dissolve in 1 litre of water? Assume that N2 exerts a partial pressure of 0.987 bar. Given that Henry’s law constant for N2 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, C6H12O6, is dissolved in 1 kg of water in a saucepan. At what temperature will water boil at 1.103 bar? (Kb for H2O is 0.52 k kg mol–1)

Que 9. Find the boiling point of a solution containing 0.520 g of glucose (C6H12O6) dissolved in 80.2 g of water. [Given: Kb 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. Kb 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 (CCl3COOH) 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. (Kb 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 (Kf) 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 Kb 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: Kf = 1.86 K kg mol–1, Atomic mass: Na = 23.0, Cl = 35.5].

Que 18. 0.6 mL of acetic acid (CH3COOH), 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 CaCl2 (molar mass 111 g mol–1) which must be added to 500 g of water to lower the freezing point by 2K, assuming CaCl2 is completely dissociated. (Kf = 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

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