# Important questions of chapter – Solutions , Class – XII

Question 1: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.

Question 2:Vapour pressure of pure water at 298 K is 23.8 mm Hg. 50 g of urea (NH2CONH2) is dissolved in
850 g of water. Calculate the vapour pressure of water for this solution and its relative lowering.

Question 3.:Boiling point of water at 750 mm Hg is 99.63°C. How much sucrose is to be added to 500 g of
water such that it boils at 100°C. Molal elevation constant for water is 0.52 K kg mol−1.

Question 4.Calculate the mass of ascorbic acid (Vitamin C, C6H8O6) to be dissolved in 75 g of acetic acid to
lower its melting point by 1.5°C. Kf = 3.9 K kg mol−1.
Question

5.:Calculate the osmotic pressure in pascals exerted by a solution prepared by dissolving 1.0 g of
polymer of molar mass 185,000 in 450 mL of water at 37°C.
Question

6.:Concentrated nitric acid used in laboratory work is 68% nitric acid by mass in aqueous solution.
What should be the M of such a sample of the acid if the density of the solution is 1.504 g mL−1?

Question 7.A solution of glucose in water is labelled as 10% w/w, what would be the molality and mole
fraction of each component in the solution? If the density of solution is 1.2 g mL−1, then what
shall be the molarity of the solution?

Question 8.How many mL of 0.1 M HCl are required to react completely with 1 g mixture of Na2CO3 and
NaHCO3 containing equimolar amounts of both?

Question 9.:A solution is obtained by mixing 300 g of 25% solution and 400 g of 40% solution by mass.
Calculate the mass percentage of the resulting solution?
Question 10.:An antifreeze solution is prepared from 222.6 g of ethylene glycol (C2H6O2) and 200 g of water.
Calculate the molality of the solution. If the density of the solution is 1.072 g mL−1, then what
shall be the molarity of the solution?

Question 11.A sample of drinking water was found to be severely contaminated with chloroform (CHCl3)
supposed to be a carcinogen. The level of contamination was 15 ppm (by mass):
(i) express this in percent by mass (ii) determine the molality of chloroform in the water sample.

Question12:State Henry’s law and mention some important applications?

Question13:The partial pressure of ethane over a solution containing 6.56 × 10−3 g of ethane is 1 bar. If
the solution contains 5.00 × 10−2 g of ethane, then what shall be the partial pressure of the gas?

Question 14:What is meant by positive and negative deviations from Raoult’s law and how is the sign of
ΔsolH related to positive and negative deviations from Raoult’s law?

Question 15:The vapour pressure of water is 12.3 kPa at 300 K. Calculate vapour pressure of 1 molal
solution of a non-volatile solute in it.

Question 16:Calculate the mass of a non-volatile solute (molar mass 40 g mol−1) which should be dissolved
in 114 g octane to reduce its vapour pressure to 80%.

Question 17.:A 5% solution (by mass) of cane sugar in water has freezing point of 271 K. Calculate the
freezing point of 5% glucose in water if freezing point of pure water is 273.15 K.

Question 18.Two elements A and B form compounds having formula AB2 and AB4. When dissolved in 20 g of
benzene (C6H6), 1 g of AB2 lowers the freezing point by 2.3 Kwhereas 1.0 g of AB4 lowers it by
1.3 K. The Kf is 5.1 Kkg mol−1. Calculate atomic masses of A and B.

Question 19.Suggest the most important type of intermolecular attractive interaction in the following pairs.
(i) n-hexane and n-octane (ii) I2 and CCl4 (iii) NaClO4 and water (iv) methanol and acetone
(v) acetonitrile (CH3CN) and acetone (C3H6O).

Question 20:Based on solute-solvent interactions, arrange the following in order of increasing solubility in
n-octane and explain – Cyclohexane, KCl, CH3OH, CH3CN. (Ans)Cyclohexane < CH3CN < CH3OH < KCl

Question 21.:Amongst the following compounds, identify which are insoluble, partially soluble and highly
soluble in water? (i) phenol (ii) toluene (iii) formic acid (iv) ethylene glycol (v) chloroform (vi) pentanol Question 22:If the solubility product of CuS is 6 × 10−16, calculate the maximum molarity of CuS in aqueous
solution….cont

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