QC Chemistry 113.1 Laboratory Manual
Version 3, Spring 2010
Practice Exercises
PRACTICE EXERCISES
Experiments 1−3
1
(1) The volumes and masses of five samples of compounds used in blending gasoline are
Sample
A
B
C
D
E
Volume (L)
0.337
0.972
0.243
0.119
0.499
Mass (g)
250.0
678.1
190.9
103.2
438.7
Identify as many of the samples as possible given
Substance
benzene
m-xylene
toluene
t-butyl alcohol
methyl t-butyl ether
isooctane
Density (g/mL)
0.8787
0.8684
0.8669
0.7856
0.7405
0.6979
(2) Calculate the volume of 10.00 g of each element in the list below and then arrange the
elements in order of decreasing volume. The density is given in parentheses.
Cu (8.92 g/mL); Ca (1.54 g/mL); Ti (4.51 g/mL); Ir (22.85 g/mL);
Au (19.32 g/mL); Fe (7.87 g/mL); S (2.07 g/mL)
(3) A silver bar has dimensions of 10.00 ± 0.04 cm × 4.00 ± 0.03 cm × 1.50 ± 0.07 cm, and the
density of silver is 10.49±0.02 g/mL. What is the mass of the bar (including uncertainty)?
(4) At 25◦ C, the density of water is 0.9970 g/mL, the density of methanol is 0.7918 g/mL, the
density of hexane is 0.6546 g/mL, and the density of diethyl ether is 0.7134 g/mL. Arrange
these compounds from strongest intermolecular interactions to weakest intermolecular
interactions. (Note: Neglect molecular size effects to work this problem.)
(5) Osmium is the densest element known (density = 22.57 g/mL). Calculate the mass in lbs
and kilograms of an osmium sphere 15 cm in diameter (about the size of a grapefruit).
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°2010
QC Chemistry and Biochemistry
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17
(6) Complete the table:
density (g/mL)
3.14
3.51
11.34
6.51
mass (g)
79.904
39.1
207.2
107.868
volume (mL)
3.42
45.5
10.28
14.0
(7) An irregularly shaped piece of magnesium with a mass of 11.81 ± 0.01 g was dropped into
a graduated cylinder partially filled with water. The magnesium displaced 6.80 ± 0.02 mL
of water. What is the density (including uncertainty) of magnesium?
(8) A graduated cylinder is filled to the 40.00 ± 0.01 mL mark with a mineral oil. The
masses of the cylinder before and after the addition of the oil are 124.966 ± 0.001 g and
159.446±0.001 g, respectively. In a separate experiment, a metal ball bearing (i.e., a metal
sphere) of mass 18.713 ± 0.001 g is placed in the cylinder and the cylinder is again filled
to the 40.00 ± 0.01 mL mark with mineral oil. The combined mass of the ball bearing and
mineral oil is 50.952 ± 0.001 g. Calculate the density (including uncertainty) and radius
of the ball bearing.
(9) Bronze is an alloy made of copper (Cu) and tin (Sn). Calculate the mass of a bronze cylinder of radius 6.44 cm and length 44.37 cm. The composition of the bronze is 79.42% Cu
and 20.58% Sn and the densities of Cu and Sn are 8.94 g/mL and 7.31 g/mL, respectively.
What assumption should you make in this calculation?
(10) A 250 mL glass bottle was filled with 242 mL of water at 20◦ C and tightly capped. It
was then left outdoors overnight, where the average temperature was −5◦ C. Predict what
would happen. The density of water at 20◦ C is 0.998 g/mL and that of ice at −5◦ C is
0.916 g/mL.
(11) Tums is a popular remedy for acid indigestion. A typical Tums tablet contains calcium
carbonate plus some nonreactive substances. When ingested, the calcium carbonate reacts
with the gastric acid (hydrochloric acid) in the stomach to give carbon dioxide gas. When
a 1.328 g tablet reacted with 40.00 mL of hydrochloric acid (density: 1.140 g/mL), carbon
dioxide gas was given off and the resulting solution weighed 46.699 g. Calculate the number
of liters of carbon dioxide gas released if its density is 1.81 g/L.
(12) Small spheres of equal mass are made of lead (density = 11.3 g/mL), silver (10.5 g/mL)
and aluminum (2.70 g/mL). Without doing a calculation, list the spheres in order from
the smallest to the largest.
(13) A 32.65 ± 0.01 g sample of a solid is placed in a flask. Toluene, in which the solid is
insoluble (i.e., the solid does not dissolve), is added to the flask so that the total volume
of the solid and the liquid together is 50.00 ± 0.01 mL. The solid and toluene together
weigh 58.58 ± 0.01 g. The density of toluene at the temperature of the experiment is
0.864 ± 0.001. What is the density (including the uncertainty) of the solid?
(14) You are given a bottle that contains 4.59 ± 0.03 mL of a metallic solid. The total mass of
the bottle and solid is 35.66 ± 0.01 g. The empty bottle weighs 14.23 ± 0.01 g. What is
the density of the solid (including the uncertainty)?
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(15) Mercury is traded by the “flask,” a unit that has a mass of 34.5 kg. What is the volume
of a flask of mercury if the density of mercury is 13.5 g/mL?
(16) A thief plans to steal a gold sphere with a radius of 28.9 cm from a museum. If the gold
has a density of 19.3 g/mL, what is the mass of the sphere? Is he likely to be able to walk
off with it unassisted?
(17) Automobile batteries contain sulfuric acid, which is commonly referred to as “battery
acid.” Calculate the number of grams of sulfuric acid in 0.500 L of battery acid if the
solution has a density of 1.28 g/mL and is 38.1% sulfuric acid by mass.
(18) A package of aluminum foil contains 50±1 ft2 of foil, which weighs 8.0±0.1 oz. Aluminum
has a density of 2.70 ± 0.01 g/mL. What is the thickness (with uncertainty) of the foil in
millimeters? (16 oz = 1 lb)
(19) Gold is alloyed (mixed) with other metals to increase the hardness. Answer the following.
(a) Consider a piece of gold jewelry that has a mass of 9.85 g and a volume of 0.675 cm3 .
If the jewelry consists of only gold (density = 19.3 g/mL) and silver (density = 10.5
g/mL), what is the percentage of gold (by mass) in the jewelry? (Assume that the
total volume is the sum of the volumes of gold and silver.)
(b) The relative amount of gold in an alloy is commonly expressed in units of karats.
Pure gold is 24-karat, and the percentage of gold in an alloy is given as a percentage
of this value. For example, an alloy that is 50% gold is 12-karat. State the purity of
the jewelry in (a) in karats.