MCQs - set II- Relative Molecular mass

MCQs Set 2
This is the second set of MCQs..you can write to me at poonamlphs@gmail.com for any queries.

1. Which of the following aqueous solutions will boil at the highest temperature? Note: all of the salts listed below are completely soluble in water.
1. A 0.10 m solution of NaCl.
2. A 0.10 m solution of Na₂SO₄.
3. A 0.10 m solution of Na₃PO₄.
4. A 0.10 m solution of K₂SO₄.
2. Which of the following pairs of properties are both colligative properties?
1. freezing point, density
2. freezing point, vapour pressure
3. boiling point, colour
4. vapour pressure, molality
3. Which of the following concentration units changes with temperature?
1. molality
2. mole fraction
3. molarity
4. mass percent
4. What is the mole fraction of water in a solution that contains 18 g of water (MW = 18 g/mol) and 92 g of ethyl alcohol (MW = 46 g/mol)?
1. 0.16
2. 0.33
3. 0.50
4. 0.87
5. What is the vapor pressure of water over a solution prepared by dissolving 100 g of sucrose (MW = 342 g/mol) in 225 g of water (MW = 18.0 g/mol) at 90^oC? The vapor pressure of pure water at 90^oC is 526 torr.
1. 0.079 torr
2. 514 torr
3. 539 torr
4. 1,184 torr
6. The melting point of pure benzene is 278.70 K and the molal freezing point depression constant is 4.90 K/molal. When 4.20 g of an unknown solute is added to 100 g of benzene, the freezing point of the solution is 277.60 K. What is the molecular weight of the unknown?
1. 226 g/mol
2. 187 g/mol
3. 128 g/mol
4. 18.7 g/mol
7. Calculate the mole fraction of acetone in the vapour above a solution prepared by dissolving 0.50 moles of acetone (P^o = 345 torr) in 1.00 mole of ethanol (P^o = 59.8 torr) at 25^oC.
1. 0.33
2. 0.50
3. 0.67
4. 0.74
8. When a solution is prepared from two volatile liquids with different vapor pressures, the vapour pressure of the solution will be:
1. greater than the vapour pressure of each of the pure liquids.
2. less than the vapour pressures of each of the pure liquids.
3. the sum of the vapour pressure of the two pure liquids.
4. somewhere between the vapor pressures of the pure liquids.
9. Which of the following statements about colligative properties is TRUE?
1. Both freezing point and boiling point INCREASE when a non- volatile solute is added to a solvent.
2. Both vapor pressure and boiling point DECREASE when a non- volatile solute is added to a solvent.
3. Colligative properties depend only upon the NUMBER of solute particles in a solution and not upon their identity.
4. None of the above statements is true.
10. The molal elevation constant is the ratio of elevation in boiling point to :-
1. Molarity
2. Molality
3. Mole fraction of the solute
4. Mole fraction of the solvent
11. A 7.00 g sample of a nonelectrolyte is dissolved in 45.0 g of water. If pure water freezes at 0.00^oC and the solution freezes at -2.56^oC, calculate the molecular weight of the nonelectrolyte. For water, k_f = 1.86 ^oC/m.
1. 11.3
2. 62.1
3. 113
4. 345
12. Which of the following aqueous solutions would have the HIGHEST freezing point? Note that all of these salts are completely soluble in water.
1. a 0.10 molal solution of sodium chloride (NaCl)
2. a 0.10 molal solution of magnesium chloride (MgCl₂)
3. a 0.10 molal solution of iron chloride (FeCl₃)
4. a 0.10 molal solution of ammonium phosphate ((NH₄)₃PO₄)
13. For a nonvolatile solute dissolved in a volatile solvent, the vapor pressure, freezing point, and boiling point:
1. are all higher for the solution than for the pure solvent.
2. change differently, with vapor pressure increasing and boiling and freezing points decreasing.
3. change differently, with boiling point increasing and vapour pressure and freezing point decreasing.
14. 0.400 mole of CCl₄ and 0.600 mole of CHCl₃ are mixed at 43^oC. The vapour pressure of pure CCl₄ at this temperature is 0.354 atm and the vapour pressure of pure CHCl₃ at this temperature is 0.526 atm. What is the vapour pressure of the solution?
1. 0.285 atm
2. 0.423 atm
3. 0.457 atm
4. 0.526 atm
15. A commercial vinegar was found to contain 4.1% BY MASS of acetic acid (CH₃COOH) in water. If the density of the vinegar is 1.01 g/mL, calculate the MOLARITY of the vinegar.
1. 0.38
2. 0.69
3. 1.1
4. 4.1
16. Calculate the PERCENT BY MASS of hydrogen peroxide (H₂O₂, MW = 34.0 g/mole) in a 5.88 M solution of H₂O₂ in water. The density of the solution is 1.00 g/mL.
1. 3.00%
2. 5.00%
3. 20.0 %
4. 30.0 %
17. Solutions which distil out without any change in composition are called:-
1. Amorphous
2. Azeotropic mixture
3. Super saturated
4. Ideal
18. Aqueous solutions of 0.004M sodium sulphate and 0.01M glucose are isotonic. The degree of dissociation of sodium sulphate is :-
1. 25%
2. 60%
3. 75%
4. 85%
19. The molal elvation constant is the ratio of elevation in boiling point to :-
1. Molarity
2. Molality
3. Mole fraction of the solute
4. Mole fraction of the solvent

20.  When 20g of Naphthoic acid(C₁₁H₈O₂) is dissolved in 50g of benzene

(Kf = 1.72Kkg/mol) , a freezing point depression of 2K is observed. The van’t Hoff factor is:-

1. 0.5
2. 1
3. 2
4. 3