Problems B
337
16. A solution containing 1.346 g of a certain protein per 100 g of water is found to
have an osmotic pressure of 9.69 cm of water at 25.0°C. Calculate the mole
weight of the protein. The density of water is 1.00 g/ml; that of Hg is 13.6
g/ml.
17. A 0.50% solution of a certain plant polysaccharide (complex plant sugar) has
an osmotic pressure of 5.40 torr at 27.0°C. Of how many simple sucrose sugar
units, C 12 H 22 O U , must this polysaccharide be composed?
18. If an aqueous sucrose (C 12 H 22 O U ) solution has an osmotic pressure of 12.5
atm at 23.0°C, what will be the vapor pressure of this solution at 23.0°C?
19. A 0.100 molal solution of acetic acid in water freezes at -0.190°C. Calculate
the percentage of ionization of acetic acid at this temperature.
20. A 0.500 molal KBr solution freezes at - 1.665°C. What is its apparent percentage of ionization at this temperature?
21. A 0.0100 molal solution of NH 3 is 4.15% ionized. What will be the freezing
point of this solution?
22. A 0.200 molal solution of Mg(NO 3 ) 2 in water freezes at -0.956°C. Calculate
the apparent percentage of ionization of Mg(NO 3 ) 2 at this temperature.
23. A solution prepared by dissolving 1.00 g of Ba(OH) 2 • 8H 2 O in 200 g of water
has a freezing point of -0.0833°C. Calculate the apparent percentage of ionization of Ba(OH) 2 at this temperature.
PROBLEMS B
24. Calculate the mole fraction and the molality of the first-named component in
each of the following solutions.
(a) 15.0% solution of ethylene glycol, C 2 H 6 O 2 , in water
(b) 7.0% solution of water in acetic acid
(c) 7.00 g of chloroform, CHC1 3 , and 30.0 g of methyl alcohol, CH 3 OH
(d) 40.0 g of ethyl alcohol, C 2 H 5 OH, and 60.0 g of acetone, C 3 H 6 O
(e) 50.0 g of formamide, HCONH 2 , and 50.0 g of water
25. What will be the freezing point of a 20.0% solution of glucose, C 6 H 12 O 6 , in
water?
26. A 20.0 g sample ofp-dichlorobenzene (C 6 H 4 C1 2 ) mothballs is added to 65.0 ml
of benzene (density = 0.879 g/ml). What will be the boiling point of this
solution?
27. A brass sample composed of 20.0% Zn and 80.0% Cu melts completely at
995.0°C; pure Cu melts at 1084.0°C. What is the molal freezing-point constant
for copper?
28. What is the boiling point of a solution of 10.0 g of diphenyl, C 12 H 10 , and 30.0 g
of naphthalene, C 10 H 8 , in 60.0 g of benzene?
337
16. A solution containing 1.346 g of a certain protein per 100 g of water is found to
have an osmotic pressure of 9.69 cm of water at 25.0°C. Calculate the mole
weight of the protein. The density of water is 1.00 g/ml; that of Hg is 13.6
g/ml.
17. A 0.50% solution of a certain plant polysaccharide (complex plant sugar) has
an osmotic pressure of 5.40 torr at 27.0°C. Of how many simple sucrose sugar
units, C 12 H 22 O U , must this polysaccharide be composed?
18. If an aqueous sucrose (C 12 H 22 O U ) solution has an osmotic pressure of 12.5
atm at 23.0°C, what will be the vapor pressure of this solution at 23.0°C?
19. A 0.100 molal solution of acetic acid in water freezes at -0.190°C. Calculate
the percentage of ionization of acetic acid at this temperature.
20. A 0.500 molal KBr solution freezes at - 1.665°C. What is its apparent percentage of ionization at this temperature?
21. A 0.0100 molal solution of NH 3 is 4.15% ionized. What will be the freezing
point of this solution?
22. A 0.200 molal solution of Mg(NO 3 ) 2 in water freezes at -0.956°C. Calculate
the apparent percentage of ionization of Mg(NO 3 ) 2 at this temperature.
23. A solution prepared by dissolving 1.00 g of Ba(OH) 2 • 8H 2 O in 200 g of water
has a freezing point of -0.0833°C. Calculate the apparent percentage of ionization of Ba(OH) 2 at this temperature.
PROBLEMS B
24. Calculate the mole fraction and the molality of the first-named component in
each of the following solutions.
(a) 15.0% solution of ethylene glycol, C 2 H 6 O 2 , in water
(b) 7.0% solution of water in acetic acid
(c) 7.00 g of chloroform, CHC1 3 , and 30.0 g of methyl alcohol, CH 3 OH
(d) 40.0 g of ethyl alcohol, C 2 H 5 OH, and 60.0 g of acetone, C 3 H 6 O
(e) 50.0 g of formamide, HCONH 2 , and 50.0 g of water
25. What will be the freezing point of a 20.0% solution of glucose, C 6 H 12 O 6 , in
water?
26. A 20.0 g sample ofp-dichlorobenzene (C 6 H 4 C1 2 ) mothballs is added to 65.0 ml
of benzene (density = 0.879 g/ml). What will be the boiling point of this
solution?
27. A brass sample composed of 20.0% Zn and 80.0% Cu melts completely at
995.0°C; pure Cu melts at 1084.0°C. What is the molal freezing-point constant
for copper?
28. What is the boiling point of a solution of 10.0 g of diphenyl, C 12 H 10 , and 30.0 g
of naphthalene, C 10 H 8 , in 60.0 g of benzene?