Chemistry Test – 1
Time: 1 Hour
Total Marks: 20
1) Ebullioscopic constant is the boiling point elevation when the concentration of
solution is ___________.
(1 M)
a. 1m
b. 1M
c. 1 mass%
d. 1 mole fraction of solute.
2) Explain the term osmosis.
(1 M)
3) State Henry’s law.
(2 M)
4) Write two differences between an ideal solution and a non-ideal solution. (2 M)
5) Calculate the freezing point of the solution when 31 g of ethylene glycol (C2H6O2)
is dissolved in 500 g of water. (Kf for water = 1.86 K kg mol–1)
(2 M)
6) When 2.56 g of sulphur was dissolved in 100 g of CS2, the freezing point lowered
by 0.383 K. Calculate the formula of sulphur (S x). (Kf for CS2 = 3.83 K kg mol−1,
Atomic mass of sulphur = 32 g mol−1)
(2 M)
7) 3.9 g of benzoic acid dissolved in 49 g of benzene shows a depression in freezing
point of 1.62 K. Calculate the van't Hoff factor and predict the nature of solute
(associated or dissociated). (Given: Molar mass of benzoic acid = 122 g mol−1, Kf for
benzene = 4.9 K kg mol−1)
(2 M)
8) The vapour pressure of pure benzene is 640mm of Hg. 2.175×10 -3 kg of nonvolatile solute is added to 39 gram of benzene. The vapour pressure of solution is
600mm of Hg. Calculate molar mass of solute. [C = 12, H = 1]
(2 M)
9) Calculate the freezing point of solution when 1.9 g of MgCl2 (M = 95 g mol−1) was
dissolved in 50 g of water, assuming MgCl2 undergoes complete ionization. (Kf for
water = 1.86 K kg mol−1)
(3 M)
10) 1.0 x10-3 Kg of urea when dissolved in 0.0985 Kg of a solvent, decreases
freezing point of the solvent by 0.211 k. 1.6x10-3 Kg of another non-electrolyte
solute when dissolved in 0.086 Kg of the same solvent depresses the freezing
point by 0.34 K. Calculate the molar mass of another solute.
(Given molar mass of urea = 60)
(3 M)