Homework 2
I
1. A 2o/o solution by mass of a non volatile solute in carbon tetrachloride (C Cl4) has
a boling point of 80.8°C. Assuming that the total masse of the solution (solute +carbon
tetrachloride) is 100 g and the normal boiling point of CCl4 at 1 atm is 76.8°C what is
the molality and the molar masse of the solute if Kb = 5.02 °C/m ?
(a) 0.79m , 25.6 g/mol
(b) 0.79m, 30 g/ mol
(c) 1.26, 25g/mol
(d) none of these
2. One automotive antifreeze consists of 40 g of ethylene glycol, C2H4(OH)2 (Molar mass
= 162 g/mol) in 400.0 g of the solution. The density of this solution is 1.072 g/mL What
is the molarity and the molality of ethylene ?
(a) 0.66 M; 0.69 m
(b) 0.60 M; 0.69 m
(c) 0.60 M; 0.62 m
(d) 0.62 M; 0.62 m (e)0.66, 0.62m (f) none of these
II
At 35oC the vapor pressure of acetone, (CH3)2CO, is 320 torr, and that of chloroform,
CHCl3, is 300 torr. Acetone and chloroform can form weak hydrogen bonds between one
another as shown below:
Cl
CH3
Cl C H O C
CH3
Cl
A solution, composed of an equal masses of acetone and chloroform, has a vapor
pressure of 250 torr at 35oC:
What would be the vapor pressure (in torr) of the solution if it exhibited ideal behavior?
(a)
340.4
(b) 314.1
(c) 98.03
(d) 98.1
III
(e) none of these
1.An aqueous solution of 160g of CuSO4(Molar mass= 160g/ mol) in 820mL of solution
has a density of 1.195 g/mL. The molality and the molarity of the solution are:
(a) 1.22 M; 1.28 m
(d)1.27M; 1.02 m
(b) 1.22 M; 1.22 m
(e) none of these
(c) 1.27; 1.044m
2. Using data from Table below:
Solvent
Normal Boiling Kb (°C/m)
Normal
Kf (°C/m)
Point (°C)
Freezing Point
Ethanol
78.4
1.22
-114.6
1.99
Chloroform
61.2
3.63
-63.5
4.68
a. Calculate the freezing point of 0.4 m glycerol in ethanol
b. Calculate the freezing point of 0.92 mol of naphthalene, C10H8, (Molar mass =
128g/mol) in 16.8 mol of chloroform, CHCl3 (Molar mass= 119.5 g/mol).
(a) -115.4°C and -64.0°C
(b)-115.4°C and -63.0°C (c)-113.8°C and -63.0°C
(d)-113.8°C and -944°C (e)-113.8°C and -64.0°C (f)-113.9°C and -63.0°C
IV
1. . The vapor pressure of pure water at 22°C is 19.8 torr. The vapor pressure of water
over a solution at 22°C containing equal numbers of moles of water and an unknown
nondissociating solute is 39.6 torr. What is the mole fraction of water, and is the solution
ideal in terms of Raoult's law?
(a) 1.0 and ideal
(b) 0.5 and ideal
(c)1.0 and non ideal (d) 0.5 and non ideal
2. A sulfuric acid solution, H2SO4, in water has a concentration of 2.45 M. The density
of water is 1.15 g/mL at 20°C. What is the molality at this temperature ?
(a) 2.45 m (b) 2.13 m
(c) 2.69 m
(d) 2.49 m (e) none of these
V
1. Lysozyme is an enzyme that breaks bacterial cell walls. A solution containing 0.150 g
of this enzyme in 210 mL of solution has an osmotic pressure of 0.953 torr at 25°C.
The molar mass of this substance is:
(a) 13.9 g/mol (b) 18.3 g/mol
(c)1.17 x 103 g/mol (d)1.39 x 104 g/mol
(e)1.41 x 106 g/mol (f) none of these
2. Which of the following form a solution ?
(i) NaCl in liquid NH3 ; (ii) C3H8 in C8H18 ; (iii) CH3Cl in CCl4;
(iv) H2O in liquid H2S
(a) i only
(b) ii only
(f) none of these
(c) i , iv only
(d) iii only
(e) i ii, iv only