Chapter 2 Solutions Textbook Solutions
i. The vapour pressure of a solution containing 2 moles of a solute in 2 moles of water (vapour pressure of pure water = 24 mm Hg) is
a. 24 mm Hg
b. 32 mm Hg
c. 48 mm Hg
d. 12 mm Hg
ii. The colligative property of a solution is
a. vapour pressure
b. boiling point
c. osmotic pressure
d. freezing point
iii. In calculating osmotic pressure the concentration of solute is expressed in
a. molarity
b. molality
c. mole fraction
d. mass percent
iv. Ebullioscopic constant is the boiling point elevation when the concentration
of solution is
a. 1m
b. 1M
c. 1 mass%
d. 1 mole fraction of solute.
v. Cryoscopic constant depends on
a. nature of solvent
b. nature of solute
c. nature of solution
d. number of solvent molecules
vi. Identify the correct statement
a. vapour pressure of solution is higher than that of pure solvent.
b. boiling point of solvent is lower than that of solution
c. osmotic pressure of solution is lower than that of solvent
d. osmosis is a colligative property.
vii. A living cell contains a solution which is isotonic with 0.3 M sugar solution.
What osmotic pressure develops when the cell is placed in 0.1 M KCl solution at body temperature?
a. 5.08 atm
b. 2.54 atm
c. 4.92 atm
d. 2.46 atm
viii. The osmotic pressure of blood is 7.65 atm at 310 K. An aqueous solution of
glucose isotonic with blood has the percentage (by volume)
a. 5.41 %
b. 3.54 %
c. 4.53 %
d. 53.4 %
ix. Vapour pressure of a solution is
a. directly proportional to the mole fraction of the solute
b. inversely proportional to the mole fraction of the solute
c. inversely proportional to the mole fraction of the solvent
d. directly proportional to the mole fraction of the solvent
x. Pressure cooker reduces cooking time for food because
a. boiling point of water involved in cooking is increased
b. heat is more evenly distributed in the cooking space
c. the higher pressure inside the cooker crushes the food material
d. cooking involves chemical changes helped by a rise in temperature.
xi. Henry’s law constant for a gas CH3Br is 0.159 moldm-3 atm at 25 0C. What is the solubility of CH3Br in water at 25 0C and a partial pressure of 0.164 atm?
a. 0.0159 mol L-1
b. 0.164 mol L-1
c. 0.026 M
d. 0.042 M
xii. Which of the following statement is NOT correct for 0.1 M urea solution and 0.05 M sucrose solution?
a. osmotic pressure exhibited by urea solution is higher than that exhibited by sucrose solution
b. urea solution is hypertonic to sucrose solution
c. they are isotonic solutions
d. sucrose solution is hypotonic to urea solution
2. Answer the following in one or two sentences
i. What is osmotic pressure?
ii. A solution concentration is expressed in molarity and not in molality while considering osmotic pressure. Why?
iii. Write the equation relating boiling point elevation to the concentration of solution.
iv. A 0.1 m solution of K2SO4 in water has freezing point of -4.3 0C. What is the value of van’t Hoff factor if Kf for water is 1.86 K kg mol-1?
v. What is van’t Hoff factor?
vi. How is van’t Hoff factor related to degree of ionization?
vii. Which of the following solutions will have higher freezing point depression
and why ?
a. 0.1 m NaCl b. 0.05 m Al2(SO4)3
viii. State Raoult’s law for a solution containing a nonvolatile solute
ix. What is the effect on the boiling point of water if 1 mole of methyl alcohol is added to 1 dm3 of water? Why?
x. Which of the four colligative properties is most often used for molecular mass determination? Why?
3. Answer the following.
i. How vapour pressure lowering is related to a rise in boiling point of solution?
ii. What are isotonic and hypertonic solutions?
iii. A solvent and its solution containing a nonvolatile solute are separated by
a semipermable membrane. Does the flow of solvent occur in both directions? Comment giving reason.
Answer:-
iv. The osmotic pressure of CaCl2 and urea solutions of the same concentration at
the same temperature are respectively 0.605 atm and 0.245 atm. Calculate van’t Hoff factor for CaCl2
v. Explain reverse osmosis.
vi. How molar mass of a solute is determined by osmotic pressure measurement?
vii. Why vapour pressure of a solvent is lowered by dissolving a nonvolatile solute into it?
viii. Using Raoult’s law, how will you show that ΔP = 0 1 P x2 ? Where x2 is the mole fraction of solute in the solution and 0 1 P vapour pressure of pure solvent.
ix. While considering boiling point elevation and freezing point depression a solution concentration is expressed in molality and not in molarity. Why?
4. Derive the relationship between degree of dissociation of an electrolyte and van’t Hoff factor
5. What is effect of temperature on solubility of solids in water? Give examples.
6. Obtain the relationship between freezing point depression of a solution containing
nonvolatile nonelctrolyte and its molar mass.
7. Explain with diagram the boiling point elevation in terms of vapour pressure
lowering.
8. Fish generally needs O2 concentration in water at least 3.8 mg/L for survival. What partial pressure of O2 above the water is needed for the survival of fish? Given the
solubility of O2 in water at 00C and 1 atm partial pressure is 2.2 × 10-3 mol/L (0.054 atm)
9. The vapour pressure of water at 20 0C is 17 mm Hg. What is the vapour pressure
of solution containing 2.8 g urea in 50 g of water? (16.17 mm Hg)
10. A 5% aqueous solution (by mass) of cane sugar (molar mass 342 g/mol) has freezing point of 271K. Calculate the freezing point of 5% aqueous glucose solution. (269.06 K)
11. A solution of citric acid C6H8O7 in 50 g of acetic acid has a boiling point elevation
of 1.76 K. If Kb for acetic acid is 3.07 K kg mol-1, what is the molality of solution?
(0.573 m)
12. An aqueous solution of a certain organic compound has a density of 1.063 gmL-1,
an osmotic pressure of 12.16 atm at 250C and a freezing point of -1.030C. What is the molar mass of the compound? (334 g/ mol)
13. A mixture of benzene and toluene contains 30% by mass of toluene. At 300C, vapour pressure of pure toluene is 36.7 mm Hg and that of pure benzene is 118.2 mm Hg. Assuming that the two liquids form ideal solutions, calculate the total pressure and partial pressure of each constituent above the solution at 300C. (86.7 mm, P = 96.5 mm)
14. At 25 0C a 0.1 molal solution of CH3COOH is 1.35 % dissociated in an aqueous solution. Calculate freezing point and osmotic pressure of the solution assuming
molality and molarity to be identical. (-0.189 0C, 2.48 atm)
15. A 0.15 m aqueous solution of KCl freezes at -0.510 0C. Calculate i and osmotic
pressure at 0 0C. Assume volume of solution equal to that of water (1.83, 6.15 atm)