Chapter
20
Multiple
Choice
Identify
the letter of the choice that best completes the statement or answers the
question.
____ 1. In a chemical change, energy can be _____.
|
a. |
created, but not destroyed |
c. |
either created or destroyed |
|
b. |
destroyed, but not created |
d. |
neither created nor destroyed |
____ 2. The two terms below that are identical in
meaning are _____.
|
a. |
calorie and Calorie |
c. |
Calorie and joule |
|
b. |
calorie and joule |
d. |
kilocalorie and Calorie |
____ 3. The main source of energy for living things
on Earth is _____.
|
a. |
combustion of fossil fuels |
c. |
solar energy |
|
b. |
oxidation of dead organisms |
d. |
geothermal energy |
____ 4. The major product formed during the process
of photosynthesis is _____.
|
a. |
carbon dioxide |
c. |
sugar |
|
b. |
water |
d. |
DNA |
____ 5. A cake is placed in a heated oven and baked.
The reactions that take place during this process are _____.
|
a. |
catalyzed |
c. |
exothermic |
|
b. |
endothermic |
d. |
inhibited |
____ 6. The energy involved in endothermic and
exothermic reactions is _____.
|
a. |
chemical |
c. |
light |
|
b. |
heat |
d. |
electrical |
____ 7. If the heat of reaction is negative, the
reaction is _____.
|
a. |
endothermic |
c. |
negative |
|
b. |
exothermic |
d. |
positive |
____ 8. Spontaneous reactions occur if energy _____
and disorder _____.
|
a. |
decreases, decreases |
c. |
increases, decreases |
|
b. |
decreases, increases |
d. |
increases, increases |
____ 9. When bowling pins at the end of an alley are
hit by a bowling ball, the entropy of the pins _____.
|
a. |
decreases |
c. |
is spontaneous |
|
b. |
increases |
d. |
stays the same |
____ 10. If a reaction results in increased energy and
increased entropy, will the reaction be spontaneous?
|
a. |
no |
c. |
yes, if the temperature is high |
|
b. |
yes |
d. |
yes, if the temperature is low |
____ 11. If 16 cans are produced from aluminum made
from ore, how many cans can be made from recycled aluminum for the same cost?
|
a. |
8 |
c. |
32 |
|
b. |
16 |
d. |
48 |
____ 12. The process that uses carbon dioxide and
water, in the presence of sunlight and chlorophyll, to form simple sugar and
oxygen is _____.
|
a. |
capillary action |
c. |
photosynthesis |
|
b. |
digestion |
d. |
respiration |
____ 13. The ultimate source of energy in the food web
is _____.
|
a. |
the sun |
c. |
light reactions |
|
b. |
photosynthesis |
d. |
the Calvin cycle |
____ 14. When photosynthesis is compared to the burning
of fossil fuels, photosynthesis is a(n) _____ efficient process.
|
a. |
less |
|
b. |
more |
|
c. |
equally |
____ 15. How can industrial processes be as efficient
as photosynthesis?
|
a. |
decrease entropy by an increase of waste
heat |
|
b. |
decrease entropy by a decrease of waste
heat |
|
c. |
increase entropy by an increase of waste
heat |
|
d. |
increase entropy by a decrease of waste
heat |
Completion
Complete
each sentence or statement.
16. Energy changes typically involve a flow of
energy from an object at high temperature to one at low temperature, an energy
transfer known as _______________.
17. In energy transfer, the total amount of energy
at the end is always the same as that at the beginning, a generalization that
is called the _______________________.
18. A unit widely used in practical situations is
equal to 0.239 J and is called the _______________.
19. Some organisms convert the inorganic
compounds, water and carbon dioxide, into carbohydrates, a process known as
_______________.
20. The amount of heat generated in a chemical
reaction is measured by a(n) _______________.
Short
Answer
21. The heats of reaction during the exothermic
formation of Al2O3 and CO2 are -1676 kJ/mol
and -394 kJ/mol, respectively. On the basis of this information, which of the
two compounds is likely to be more stable?
22. Although electricity is often the most
convenient form of energy to use, it is almost never the most efficient
overall. Why?
23. When energy is wasted during an industrial
process, what actually happens to that energy?
24. Explain why industrial processes can never be
100 percent efficient, in spite of the fact that energy is conserved in all
processes.
The graph in Figure 20-1 shows the
absorption of light by a chlorophyll molecule at various wavelengths. Answer
the following questions about this graph.
25. At what regions of wavelength does the
chlorophyll molecule absorb light energy most strongly? Least strongly?
26. How does this graph explain the color of
chlorophyll?
27. The vertical axis on the graph is labeled
"energy absorbed." Why is the amount of oxygen produced during
photosynthesis at each wavelength roughly proportional to the energy absorbed
at each wavelength?
The graph in Figure 20-2 shows energy
changes that take place when hydrogen and iodine react to form hydrogen iodide.
Answer the following questions by referring to this graph.
28. Estimate the energy possessed by the products
of the reaction.
29. Estimate the activation energy required for
the reaction to occur.
30. Is this reaction endothermic or exothermic?
What is the heat of reaction?
Problem
31. How much heat in kilojoules is released when
25.0 g of water is cooled from 85.0ēC to 40.0ēC?
32. A 1.5-g sample of methane (CH4) gas
is burned completely in a calorimeter that contains 500.0 g of water. The
temperature of the water rises from 22.00ēC to 23.50ēC. How much heat in
kilojoules was given off in the reaction? How much heat would 1.00 mol of the
gas produce when burned?