Problems B
171
47. A mixture of copper and zinc is analyzed for the percentage of zinc by adding
an excess of HCl and collecting the evolved H 2 over water. (Copper will not
react with HCl.) The volume of H 2 collected is 229.5 ml at a barometric
pressure of 732 torr. The temperature is 29°C. What volume would the H 2
occupy at standard conditions, dry?
48. In some recent work at the Bell Telephone Research Laboratory, a low
pressure of I0~" torr of mercury was used. This is an unusually low pressure,
one not easily obtained. Calculate the number of molecules still remaining in 1
ml of gas at this pressure at 27°C.
49. A 1 g sample of helium occupies 5.6 liters at standard conditions. What will be
its weight when expanded to a pressure of 0.10 atm?
50. What volume will 5.00 g of methyl alcohol, CH 3 OH, occupy at 720 torr and
98°C?
51. What is the weight of 420 ml of NH 3 measured at 735 torr and 27°C?
52. What volume will be occupied by 2.50 g of CO measured over water at 27°C
and 725 torr?
53. What is the molecular weight of a gas if 365 ml of it measured over water at
727 torr and 30°C weighs 1.42 g?
54. What is the density of NH 3 gas at 78°F and 741 torr?
55. Calculate the density of C 2 H 6 (a) at standard conditions; (b) at 725 torr and
27°C, dry.
56. What is the apparent mole weight of a gas mixture whose composition by
2?
57. If 0.670 g of a vapor at 100°C and 735 torr has a volume of 249 ml, what must
its mole weight be?
58. A mixture of gases contained in a vessel at 1.30 atm is found to be 60.0% NH 3 ,
25.0% NO, and 15.0% N 2 by volume.
(a) What is the partial pressure of each gas?
(b) A bit of solid P 4 O 10 is added to remove the NH 3 . Calculate the resulting
total pressure, and the partial pressures of the remaining gases.
59. A gas mixture containing CO 2 is subjected, at 1.00 atm, to the action of KOH,
which removes the CO 2 . In this way, the CO 2 is found to be 27.0% by volume
of the mixture. What is the partial pressure of CO 2 in the mixture?
60. A vessel, whose volume is 205.3 ml and whose weight evacuated is 5.3095 g +
a tare flask, is filled with an unknown gas to a pressure of 750 torr at a
temperature of 27°C. It is then cleaned, wiped with a damp cloth, and hung in
the balance case to come to equilibrium with the tare vessel. The tare vessel
has about the same surface area and is needed to minimize effects of surface
moisture. The second weighing is 5.6107 g + the tare flask. What is the mole
weight of the gas?
171
47. A mixture of copper and zinc is analyzed for the percentage of zinc by adding
an excess of HCl and collecting the evolved H 2 over water. (Copper will not
react with HCl.) The volume of H 2 collected is 229.5 ml at a barometric
pressure of 732 torr. The temperature is 29°C. What volume would the H 2
occupy at standard conditions, dry?
48. In some recent work at the Bell Telephone Research Laboratory, a low
pressure of I0~" torr of mercury was used. This is an unusually low pressure,
one not easily obtained. Calculate the number of molecules still remaining in 1
ml of gas at this pressure at 27°C.
49. A 1 g sample of helium occupies 5.6 liters at standard conditions. What will be
its weight when expanded to a pressure of 0.10 atm?
50. What volume will 5.00 g of methyl alcohol, CH 3 OH, occupy at 720 torr and
98°C?
51. What is the weight of 420 ml of NH 3 measured at 735 torr and 27°C?
52. What volume will be occupied by 2.50 g of CO measured over water at 27°C
and 725 torr?
53. What is the molecular weight of a gas if 365 ml of it measured over water at
727 torr and 30°C weighs 1.42 g?
54. What is the density of NH 3 gas at 78°F and 741 torr?
55. Calculate the density of C 2 H 6 (a) at standard conditions; (b) at 725 torr and
27°C, dry.
56. What is the apparent mole weight of a gas mixture whose composition by
2?
57. If 0.670 g of a vapor at 100°C and 735 torr has a volume of 249 ml, what must
its mole weight be?
58. A mixture of gases contained in a vessel at 1.30 atm is found to be 60.0% NH 3 ,
25.0% NO, and 15.0% N 2 by volume.
(a) What is the partial pressure of each gas?
(b) A bit of solid P 4 O 10 is added to remove the NH 3 . Calculate the resulting
total pressure, and the partial pressures of the remaining gases.
59. A gas mixture containing CO 2 is subjected, at 1.00 atm, to the action of KOH,
which removes the CO 2 . In this way, the CO 2 is found to be 27.0% by volume
of the mixture. What is the partial pressure of CO 2 in the mixture?
60. A vessel, whose volume is 205.3 ml and whose weight evacuated is 5.3095 g +
a tare flask, is filled with an unknown gas to a pressure of 750 torr at a
temperature of 27°C. It is then cleaned, wiped with a damp cloth, and hung in
the balance case to come to equilibrium with the tare vessel. The tare vessel
has about the same surface area and is needed to minimize effects of surface
moisture. The second weighing is 5.6107 g + the tare flask. What is the mole
weight of the gas?