Problems A
97
6. A glass bulb with a stopcock weighs 54.9762 g when evacuated, and 54.9845 g
when filled with a gas at 25°C. The bulb will hold 50.0 ml of water. What is the
density of the gas at 25°C?
7. Mercury (density = 13.54 g/ml) is sold by the "flask," which holds 76 Ib of
mercury. If the cost is $1130 per flask, how much does 1 ml of mercury cost?
8. (a) A column of mercury (density = 13.54 g/ml) 730 mm high in a tube of 8
mm inside diameter is needed to balance a gas pressure. What weight of
mercury is in the tube?
(b) If the same gas pressure were balanced by mercury in a tube of 16 mm
inside diameter, what weight of mercury would be needed?
9. In normal whole blood there are about 5.4 x 10" red cells per milliliter. The
volume of a red cell is about 90 fj,m ', and the density of a red cell is 1.096 g/ml.
How many pints of whole blood would we need in order to collect 8 oz
(avoirdupois) of red cells?
10. How far (in centimeters) does a 1 cm cube of wood stick out of the water if its
density is 0.85 g/ml?
11. A piece of Invar (density = 8.00 g/ml) weighs 15.4726 g in air and 13.9213 g
when suspended in liquid nitrogen at a temperature of - 196°C. What is the
density of liquid nitrogen at that temperature? (Invar has a very small coefficient of thermal expansion, and its change in density with temperature may be
neglected in this problem.)
12. The weight of a metal sample is measured by finding the increase in weight of
a volumetric flask when the metal sample is placed in it. The volume of the
metal sample is measured by finding how much less water the volumetric flask
holds when it contains the metal sample. Compute the density of the metal
sample from the following data, assuming that the density of water is 1.000
g/ml.
Weight of empty flask = 26.735 g
Weight of flask + sample = 47.806 g
Weight of flask + sample + water = 65.408 g
Weight of flask + water (no sample) = 50.987 g
13. (a) Repeat the calculations of Problem 12, using an accurate density value for
water (Table 7-1) and assuming the measurements were made at 27°C.
(b) In which decimal place does it make a significant difference if the accurate
density for water is used instead of 1 g/ml?
14. A chemical is soluble in water but insoluble in benzene. As a consequence,
benzene may be used to determine its density. The density of benzene is 0.879
g/ml at 20°C. From the following data (obtained as in Problem 12), compute
the density of the sample.
97
6. A glass bulb with a stopcock weighs 54.9762 g when evacuated, and 54.9845 g
when filled with a gas at 25°C. The bulb will hold 50.0 ml of water. What is the
density of the gas at 25°C?
7. Mercury (density = 13.54 g/ml) is sold by the "flask," which holds 76 Ib of
mercury. If the cost is $1130 per flask, how much does 1 ml of mercury cost?
8. (a) A column of mercury (density = 13.54 g/ml) 730 mm high in a tube of 8
mm inside diameter is needed to balance a gas pressure. What weight of
mercury is in the tube?
(b) If the same gas pressure were balanced by mercury in a tube of 16 mm
inside diameter, what weight of mercury would be needed?
9. In normal whole blood there are about 5.4 x 10" red cells per milliliter. The
volume of a red cell is about 90 fj,m ', and the density of a red cell is 1.096 g/ml.
How many pints of whole blood would we need in order to collect 8 oz
(avoirdupois) of red cells?
10. How far (in centimeters) does a 1 cm cube of wood stick out of the water if its
density is 0.85 g/ml?
11. A piece of Invar (density = 8.00 g/ml) weighs 15.4726 g in air and 13.9213 g
when suspended in liquid nitrogen at a temperature of - 196°C. What is the
density of liquid nitrogen at that temperature? (Invar has a very small coefficient of thermal expansion, and its change in density with temperature may be
neglected in this problem.)
12. The weight of a metal sample is measured by finding the increase in weight of
a volumetric flask when the metal sample is placed in it. The volume of the
metal sample is measured by finding how much less water the volumetric flask
holds when it contains the metal sample. Compute the density of the metal
sample from the following data, assuming that the density of water is 1.000
g/ml.
Weight of empty flask = 26.735 g
Weight of flask + sample = 47.806 g
Weight of flask + sample + water = 65.408 g
Weight of flask + water (no sample) = 50.987 g
13. (a) Repeat the calculations of Problem 12, using an accurate density value for
water (Table 7-1) and assuming the measurements were made at 27°C.
(b) In which decimal place does it make a significant difference if the accurate
density for water is used instead of 1 g/ml?
14. A chemical is soluble in water but insoluble in benzene. As a consequence,
benzene may be used to determine its density. The density of benzene is 0.879
g/ml at 20°C. From the following data (obtained as in Problem 12), compute
the density of the sample.