Name ________________________________________ Class _________________ Date _______________
4
PROBLEM SOLVING IN CHEMISTRY
PRACTICE PROBLEMS
In your notebook solve the following problems. Use the three-step problem-solving
approach.
SECTION 4.1 WHAT DO I DO NOW?
1. One morning while hiking near Winslow, AZ, you find an unusual yellowcolored rock. Upon inspection, you discover it feels heavier than other rocks.
You take it home and measure its mass and volume to be 289.5 g and 15.0 cm3,
respectively. What is the density of this rock?
a. ANALYZE (List the knowns and unknown)
Knowns:
Unknown:
volume of rock 5
density 5 ? g/cm3
mass of rock 5
b. CALCULATE (Solve for the unknown.)
Use an equation that relates your knowns and unknown.
mass
density 5 }}
volume
Substitute known values for mass and volume and carry out calculations.
density 5
c. EVALUATE (Does the result make sense?)
When you evaluate your answer do the following checks.
Double check your numerical calculations.
Do your final units agree with the unknown units?
Does the numerical answer make sense?
Can you identify what this rock may, in fact, be?
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2. A large piece of cork has a volume of 1000.0 cm3 and a mass of 240.0 grams.
What is the density of the cork?
3. A type of wood known as white pine has a density equal to 0.50 g/cm3. What is
the mass of a block of white pine that has the dimensions 5.0 cm by 10.0 cm by
200.0 cm?
4. A piece of ice (frozen water) has a mass of 9.2 g and a volume of 10.0 cm3.
a. What is the density of the ice?
b. Would this ice float in liquid water? (density of liquid water 5 1.0 g/cm3)
c. Would the ice float in gasoline? (density of gasoline 5 0.7 g/cm3)
5. What is the volume, in cm3, of a sample of mercury that has a mass of 2000.0 g?
(density of mercury 5 13.6 g/cm3)
6. The density of silicon is 2.33 g/cm3. What is the volume of a piece of silicon that
has a mass of 83.8 g?
7. Helium boils at 4 K. What is this temperature in degrees Celsisus?
Review Module / Chapters 1–4
83
Name ________________________________________ Class _________________ Date _______________
8. A nugget of gold displaces 0.950 cm3 of water. If a jeweler offers $8.00/g for the
nugget, how much money is the nugget worth? (density of gold 5 19.3 g/cm3)
9. The boiling point of ethanol is 78 8C. What is this temperature on the Kelvin
scale?
SECTION 4.2 SIMPLE CONVERSION PROBLEMS
1. The population of San Francisco is 750 000 in an area of 49 square miles. What
is the population density in San Francisco? Express your answer in people per
acre. (1 mi2 5 640 acres)
2. A sugar-free powdered drink mix sells for $2.99 per can. Each can of the mix
contains 50.2 g of powder, which, when added to water, will make 8 quarts of
drink. What is the cost of the powdered drink mix in dollars/lb? (454 g 5 1 lb)
3. The density of water is 1.00 g/cm3. What is the density of water expressed in
lb/ft3? (1 lb 5 454 g; 2.54 cm 5 1 in.)
4. The dimensions of a room are 12 ft by 15 ft. How much will it cost to carpet the
total area of this room if the cost of the carpet is $8.00/yd2?
5. How fast is 60 miles per hour, expressed in kilometers per hour (km/h)?
(1 mi 5 1.609 km)
6. A whole chicken sells for $7.06 and it has a mass of 1.5 kg. A beef shank sells for
$10.00 with a mass of 2.5 kg. Compare the per pound cost for each item. (1 kg 5
2.2 lb)
7. How many seconds are there in a day? (1 day 5 24 h)
SECTION 4.3 MORE-COMPLEX PROBLEMS
1. The speed limit on a certain highway is 72 km/h. What is this speed in cm/s?
2. How many cubic decimeters are contained in one cubic meter?
3. Astronomers often use the unit light-year to express intergalactic distances. If
light travels 3.00 3 1010 cm/s, and one year is defined as 365 days, how many
kilometers does light travel in one year?
5. There are 7.0 3 106 red blood cells in 1.0 mm3 of blood. How many red blood
cells are in 1.0 L of blood?
6. An automobile can travel 40.0 miles on one gallon of gasoline. How many
kilometers per liter is this? (1.61 km 5 1 mi; 1 L 5 0.264 gal)
7. Suppose that gold is selling at $375/ounce. How many milligrams of gold could
you buy for one cent? (16 oz 5 1 lb; 1 lb 5 454 g)
84
Review Module / Chapters 1–4
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4. Gold has a density of 19.3 g/cm3. What is the mass, in kilograms, of one cubic
meter of gold?