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# Top 10 Question for CBSE Board Exam - 01, Class XII CBSE Chapter – Solution

Top 10 Question for Board Exam - 01

Chapter – Solution

1. Define the following terms molarity, molality and mole fraction. What is the effect of temperature change on molarity and molality in a solution?

2. Calculate the molarity of 9.8% (w/W) solution of H2SO4 if the density of the solution is 1.02 g mL–1. (Ans – Molarity = 1.02 mole/L)

3. An antifreeze solution is prepared from 222.6 g of ethylene glycol (C2H4(OH)2) and 200 g of water. Calculate the molality of the solution. If the density of this solution be 1.072 g mL–1 what will be the molality of the solution? (Ans – Molality = 17.95 molal, Molarity = 9.11 Molar)

4. State Raoult’s law for a solution containing volatile components. Name the solution which follows Raoult’s law at all concentrations and temperatures.

5. ­The vapour pressure of pure liquids A and B are 450 and 700 mm Hg respectively, at 350 K. Find out the composition of the liquid mixture if total vapour pressure is 600 mm Hg. Also find the composition of the vapour phase. (Ans – In liquid phase Mole Fraction of A = 0.4 and B = 0.6 and in Vapour phase A = 0.3 and B = 0.7)

6. What is meant by positive deviations from Raoult’s law? Give an example. What is the sign of ∆Hmix for positive deviation?

7. What is meant by colligative properties? Write its type.

8. Blood cells are isotonic with 0.9% sodium chloride solution. What happens if we place blood cells in a solution containing (i) 1.2% sodium chloride solution? (ii) 0.4% sodium chloride solution?

9. Calculate the mass of compound (molar mass = 256 g mol–1) to be dissolved in 75 g of benzene to lower its freezing point by 0.48 K. (Kf = 5.12 K kg mol–1). (Ans – 1.8 gms)

18 g of glucose, C6H12O6 (Molar mass = 180 g mol–1) is dissolved in 1 kg of water in a sauce pan. At what temperature will this solution boil? (Kb for water = 0.52 K kg mol–1, boiling point of pure water = 373. 15 K) (Ans – 373.2 K)