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Important 5mark -chapter 9,10

11th Standard

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Chemistry

Use blue pen Only

Time : 00:30:00 Hrs
Total Marks : 50

10 x 5 = 50
1. Calculate the proportion of O2 and N2 dissolved in water at 298 K. When air containing 20% O2 and 80% N2 by volume is in equilibrium with it at 1 atm pressure. Henry’s law constants for two gases are KH(O2) = 4.6 x 104 atm and KH (N2) = 8.5 x 104 atm.

2. Calculate the mole fractions of benzene and naphthalene in the vapour phase when an ideal liquid solution is formed by mixing 128 g of naphthalene with 39 g of benzene. It is given that the vapour pressure of pure benzene is 50.71 mmHg and the vapour pressure of pure naphthalene is 32.06 mmHg at 300 K.

3. 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?

4. 2.56 g of Sulphur is dissolved in 100g of carbon disulphide. The solution boils at 319. 692 K. What is the molecular formula of Sulphur in solution The boiling point of CS2 is 319. 450K. Given that Kb for CS2 = 2.42 K Kg mol-1.

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. 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)?

7. A sample of 12 M Concentrated hydrochloric acid has a density 1.2 gL–1 Calculate the molality

8. Henry’s law constant for solubility of methane in benzene is 4.2 x 10-5 mm Hg at a particular constant temperature At this temperature. Calculate the solubility of methane at i) 750 mm Hg ii) 840 mm Hg

9. 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.

10. The vapour pressure of pure benzene (C6H6) at a given temperature is 640 mm Hg. 2.2 g of non-volatile solute is added to 40 g of benzene. The vapour pressure of the solution is 600 mm Hg. Calculate the molar mass of the solute?