#### Solutions Three Marks Questions

11th Standard

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Chemistry

Time : 00:45:00 Hrs
Total Marks : 30
10 x 3 = 30
1. If 5.6 g of KOH is present in (a) 500 mL and (b) 1 litre of solution, calculate the molarity of each of these solutions.

2. Describe how would you prepare the following solution from pure solute and solvent
(a) 1 L of aqueous solution of 1.5 M CoCl2.
(b) 500 mL of 6.0% (V/V) aqueous methanol solution.

3. Vapour pressure of a pure liquid A is 10.0 torr at 27°C. The vapour pressure is lowered to 9.0 torr on dissolving one gram of B in 20 g of A. If the molar mass of A is 200 then calculate the molar mass of B.

4. An aqueous solution of 2% nonvolatile solute exerts a pressure of 1.004 bar at the boiling point of the solvent. What is the molar mass of the solute when PA is 1.013 bar?

5. Ethylene glycol (C2H6O2) can be at used as an antifreeze in the radiator of a car. Calculate the temperature when ice will begin to separate from a mixture with 20 mass percent of glycol in water used in the car radiator. Kf for water = 1.86 K Kg mol-1 and molar mass of ethylene glycol is 62 g mol-1.

6. 2g of a non electrolyte solute dissolved in 75 g of benzene lowered the freezing point of benzene by 0.20 K. The freezing point depression constant of benzene is 5.12 K Kg mol-1. Find the molar mass of the solute.

7. What is the mass of glucose (C6 H12O6) in it one litre solution which is isotonic with 6 g L-1 of urea (NH2 CO NH2)?

8. The depression in freezing point is 0.24K obtained by dissolving 1g NaCl in 200g water. Calculate van’t-Hoff factor. The molal depression constant is 1.86 K Kg mol-1.

9. 0.2 m aqueous solution of KCl freezes at -0.68ºC calculate van’t Hoff factor. kf for water is 1.86 K kg mol-1.

10. The observed depression in freezing point of water for a particular solution is 0.093o C. Calculate the concentration of the solution in molality. Given that molal depression constant for water is 1.86 KKg mol-1.