Chapter 10:
Energy Sources
Practice Test
1.
A gallon of gasoline contains about 2800 g of gasoline. If burning one gram of gasoline releases about 48 kJ of energy, how much energy is released when a gallon of gasoline is burned? (1 kJ = 1000 J)
a.
134,400 kJ
b.
13,440 kJ
c.
58.3 kJ
d.
1,344,000 kJ
Hint
2.
Suppose the number of uranium-235 nuclei that are split doubles at each stage of a chain reaction. If the chain reaction starts with one nucleus being split in the first stage, how many nuclei will have been split after 6 stages?
a.
12
b.
6
c.
32
d.
10
Hint
3.
About 85% of the energy used in the U.S. comes from fossil fuels. How many times greater is the amount of energy used from fossil fuel than the amount used from all other energy sources?
a.
15 times
b.
0.2 times
c.
5.7 times
d.
85 times
Hint
4.
From 1970 to 1995 the carbon dioxide concentration in Earth's atmosphere increased from about 325 parts per million to about 360 parts per miilion. What was the percentage change in the concentration of carbon dioxide?
a.
110.8%
b.
9.7%
c.
90.3%
d.
10.8%
Hint
5.
You heat a cup of water in a 750 W microwave oven for 40 s, and warm the water by 20°C. If it takes about 20 kJ of energy to raise the temperature of a cup of water by 20°C, what is the efficiency of the microwave oven?
a.
1%
b.
3.8%
c.
67%
d.
50%
Hint
6.
An automobile engine converts the energy released by burning gasoline into mechanical energy with an efficiency of about 25%. If burning one kg of gasoline releases about 48,000 kJ of energy, how much mechanical energy is produced by the engine when 1 kg of gasoline is burned?
a.
60,000 kJ
b.
12,000 kJ
c.
36,000 kJ
d.
1,200,000 kJ
Hint
7.
What is the overall efficiency of a hydroelectric plant if the process of falling water turning a turbine is 80% efficient, the turbine spinning an electric generator is 95% efficient, and the transmission through power lines is 90% efficient?
a.
76%
b.
265%
c.
80%
d.
68%
Hint
8.
A nuclear reactor contains 100,000 kg of enriched uranium. About 4% of the enriched uranium is uranium-235. What is the mass of the isotope uranium-235 in the reactor core??
a.
4000 kg
b.
40 kg
c.
40,000 kg
d.
400 kg
Hint
9.
On average, solar energy strikes Earth's surface with an intensity of about 200 W/m². If solar cells are 10% efficient, how large an area would have to be covered by solar cells to generate enough electrical power to light a 100 W light bulb?
a.
2 m²
b.
10 m²
c.
5 m²
d.
20 m²
Hint
10.
When a certain
235
92
U nucleus is struck by a neutron, it forms the two nuclei
91
36
Kr and
142
56
Ba. How many neutrons are emitted when this occurs?
a.
3
b.
2
c.
1
d.
4
Hint
