Class XII
CHAPTER: Solutions (Extra questions for Board examination)
1. How does the temperature and pressure affect solubility of
i. Solid Solute in liquid
ii. Gases in liquid
2. Define Henry’s law. Two gases A and B have Henry’s law constant 60.2
Kbar and 30.5 Kbar, out of them which on will be highly soluble?
3. Which of the following is a dimensionless quantity : molarity, molality or
mole fraction?
4. State the conditions which must be satisfied if an ideal solution is to be
formed.
5. A mixture of chlorobenzene and bromobenzene forms nearly ideal
solution but a mixture of chloroform and acetone does not. Why?
6. N2 and O2 gases have KH values 76.48 kbar and 34.86 kbar respectively
at 293 K temperature. Which one of these will have more solubility in
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water?
7. Under what condition molality and molarity of a solution are identical.
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Explain with suitable reason.
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8. What is a ideal solution?
9. Define Raoult’s law.
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10.What will happen to the boiling point of the solution formed on mixing
two miscible liquids showing negative deviation from Raoult’s law?
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11.Liquid ‘Y’ has higher vapour pressure than liquid ‘X’, which of them will
have higher boiling point?
12.When 50 mL of ethanol and 50 mL of water are mixed, predict whether
the volume of the solution is equal to, greater than or less than 100 mL.
Justify.
13.Which type of deviation is shown by the solution formed by mixing
cyclohexane and ethanol?
14.A and B liquids on mixing produce a warm solution. Which type of
deviation from Raoult’s law is there?
15.What is reverse osmosis? Give one large scale use of it.
16.What is the maximum value of van’t Hoff factor for Na2SO4 . 10H2O?
17.What is the value of van’t Hoff factor if solute molecules undergo
dimerisation.
18.Give two examples each of a solution :
A. showing positive deviation from Raoult’s Law.
B. showing negative deviation from Raoult’s Law.
19.Define azeotropes with one example of each type.
20.The vapour pressure curve for three solutions having the same non-
volatile solute in the same solvent is shown. The curves are parallel to
each other and do not intersect. What is the correct order of the
concentrations of the solutions?
21.Show that the relative lowering of vapour pressure of a solvent is a
colligative property.
22.Given reason for the following :–
A. Aquatic species are more comfortable in cold waters than in warm
waters.
B. To avoid bends scuba divers use air diluted with helium.
C. Cold drinks bottles are sealed under high pressure of CO2.
23.Why should a solution of a non-volatile and non-eletrolyte solute boil at a
higher temperature? Explain with the help of a diagram. Derive the
relationship between molar mass and elevation in boiling point.
24.Give reasons for the following :–
A. RBC swells up and finally burst when placed in 0.1% NaCl solution.
B. When fruits and vegetables that have been dried are placed in water,
they slowly swell and return to original form.
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25.15.0 g of an unknown molecular substance was dissolved in 450 g of
water. The resulting solution was fund to freeze at –0.34°C. What is the
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molar mass of this substance? (Kf for water = 1.86 K kg mol–1).
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26.How much urea (mol. mass 60 g mol–1) must be dissolved in 50g of
water so that the vapour pressure at the room temperature is reduced by
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25%? Also calculate the molality of the solution obtained.
27.Define osmotic pressure.
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A. Why osmotic pressure is preferred over other colligative properties for
the determination of molecular masses of macromolecules?
B. What is the molar concentration of particles in human blood if the
osmotic pressure is 7.2 atm at normal body temperature of 37°C?
28.Calculate the mass percentage of benzene (C6H6) and carbon tetrachloride
(CCl4), If 22g of benzene is dissolved in 122g of carbon tetrachloride.
29.The mole fraction of CH3OH in an aqueous solution is 0.02 and density
of solution 0.994 g cm–3. Determine the molality and molarity.
30.6 × 10–3 g oxygen is dissolved per kg of sea water. Calculate the ppm of
oxygen in sea water.
31.Two liquids X and Y on mixing form an ideal solution. The vapour
pressure of the solution containing 2 mol of X and 1 mol of Y is 550 mm
Hg. But when 4 mol of X and 1 mole of Y are mixed, the vapour pressure
of solution thus formed is 560 mm Hg. What will be the vapour pressure
of pure X and pure Y at this temperature?
32.Calculate the amount of NaCl which must added to one kg of water so
that the freezing point is depressed by 3K. Given Kf = 1.86 K kg mol–1,
Atomic mass : Na = 23, Cl = 35.5).
33.Osmotic pressure of a 0.0103 molar solution of an electrolyte was found
to be 0.75 atm at 27°C. Calculate Van’t Hoff factor.
34.The vapour pressure of pure liquids A and B are 450 and 750 mm Hg
respectively, at 350K. Find out the composition of the liquid mixture if
total vapour pressure is 600 mm Hg. Also find the composition of the
vapour phase.
35.An aqueous solution of 2% non-volatile solute exerts a pressure of 1.004
bar at the normal boiling point of the solvent. What is the molar mass of
the solute?
36.For a dilute solution containing 2.5 g of a non-volatile non-electrolyte
solute in 100 g of water, the elevation in boiling point at 1 atm pressure is
2°C. Assuming concentration of solute is much lower than the
concentration of solvent, determine the vapour pressure (mm of Hg) of
the solution.
37.Two liquids A and B have vapour pressure in the ratio P0A:P0B =2:3 at a
certain temperature. Assume A and B form an ideal solution and the ratio
of mole fractions of A to B in the vapour phase is 1: 3, then what is the
mole fraction of A in the solution at the same temperature?
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38.Benzene and toluene form a nearly ideal solution. At a certain
temperature, calculate the vapour pressure of solution containing equal
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moles of the two substances. [Given : P°Benzene = 150 mm of Hg,
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P°Toluene = 55 mm of Hg].
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