CHEMISTRY
A. Henry’s Law (10 Numericals)
Easy (4)
1. The Henry’s law constant for a gas is 77×10³ atm. What is its solubility in water at 298 K
under 1 atm pressure?
2. A gas has a Henry’s constant of 50 kPa. If its solubility is 0.002 mol/L at 1 kPa, what will it
be at 100 kPa?
3. CO₂ has a Henry’s law constant of 1.67×10⁸ Pa. What is its solubility in water at 5 atm
pressure?
4. The solubility of O₂ is 0.031 mol/L at 1 atm. What will be the solubility at 3 atm?
Moderate (3)
5. A gas has a Henry’s law constant of 1.5×10⁵ Pa. If its solubility in water is 0.02 mol/L,
calculate the partial pressure of the gas.
6. A gas has a Henry’s law constant of 6.0×10⁴ atm. At what pressure will its solubility be
0.01 mol/L?
7. In a cold drink, the solubility of CO₂ is 0.15 mol/L and the Henry’s constant at the
temperature is 3×10⁵ Pa. Calculate the partial pressure of CO₂.
Hard (3)
8. Henry’s law constant is 2.5×10⁵ atm. If 3.5 g of a gas (molar mass = 28 g/mol) dissolves in
500 mL of water, calculate the partial pressure of the gas.
9. Gases A and B have Henry’s constants 1.8×10⁵ Pa and 2.5×10⁵ Pa respectively. Which gas
is more soluble and why?
10. A mixture of gases is bubbled through water. Gas X has solubility 0.045 mol/L at 2 atm,
while Y has 0.025 mol/L at 3 atm. Which gas has the lower Henry’s constant and explain?
B. Raoult’s Law (10 Numericals)
Easy (4)
1. A solution is prepared by mixing 60 g of urea (non-volatile) in 180 g of water. Calculate
the relative lowering of vapour pressure.
2. Vapour pressure of pure water at 298 K is 23.8 mmHg. What is the vapour pressure of a
solution containing 1 mol of glucose in 1 kg of water?
3. A solution contains 0.5 mol of solute and 1.5 mol of solvent. What is the relative lowering
of vapour pressure?
4. A liquid solution has a vapour pressure of 90 mmHg, and the pure solvent has a vapour
pressure of 100 mmHg. What is the mole fraction of solute?
Moderate (3)
5. A solution is made by dissolving 10 g of a non-volatile solute in 90 g of water. The vapour
pressure of water decreases by 0.4 mmHg. Calculate the molar mass of the solute
6. The vapour pressure of benzene is 100 mmHg. A non-volatile solute is added such that
mole fraction of benzene becomes 0.8. Calculate new vapour pressure.
7. 2 mol of ethanol is mixed with 1 mol of water. Vapour pressures of pure ethanol and
water are 44 mmHg and 54 mmHg respectively. Calculate total vapour pressure of the
solution.
Hard (3)
8. 0.5 mol of a non-volatile solute is added to 9.5 mol of water. Calculate the relative
lowering of vapour pressure and final vapour pressure if pure water has 25 mmHg vapour
pressure.
9. Two liquids A and B have vapour pressures 200 mmHg and 150 mmHg respectively. In a
solution, the mole fraction of A is 0.6. Find total vapour pressure and partial pressures of A
and B.
10. A binary solution has mole fraction of component A as 0.4. Vapour pressures of pure A
and B are 120 mmHg and 80 mmHg respectively. Calculate total vapour pressure and
identify which component has higher escaping tendency.
