CHAPTER
6
Review
SUGGESTED ANSWERS
WHAT DO YOU REMEMBER?
1. (a)
(f)
2. (a)
(b)
2; (b) 1; (c) 3; (d) 2; (e) 5
ZnS is a solid, oxygen is a gas, ZnO is a solid, and SO2 is a gas.
Sample answer: This may occur in a refinery where natural gas is burned off of petroleum products.
The sooty residue is carbon—this is produced when incomplete combustion occurs.
This is an incomplete combustion reaction.
WHAT DO YOU UNDERSTAND?
3. (a)
4.
(b)
A double-displacement reaction has two compounds.
(c)
A combustion reaction has oxygen and a fuel.
(d)
A decomposition reaction has only one compound.
(e)
A single-displacement reaction has an element and a compound.
Chemical reactions obey the law of conservation of mass, which states that matter is not created or
destroyed. A chemical equation must be balanced in order to conserve mass.
5. (a)
6.
An aqueous (aq) solution is one in which water is involved. A liquid (l) can be any liquid, not
necessarily water.
(b)
I predict that I would see bubbles created (the oxygen that is produced).
(c)
The reaction would be complete when no more bubbles are created and when there is no more
hydrogen peroxide.
(d)
The mass will decrease even though mass is conserved. Unless the experiment was performed in a
closed container, the oxygen produced will escape into the air, leaving behind just the water.
The coating of oil forms a barrier to keep oxygen from reaching the metal. Without oxygen, the metal
cannot rust, or oxidize.
7. (a)
404
A synthesis reaction has two elements.
2K 2O → 4K 1 O2; decomposition
(b)
2Na 1 I2 → 2NaI; synthesis
(c)
Cu(NO3)2 1 2NaOH → Cu(OH)2 1 2NaNO3; double displacement
(d)
2KClO3 → 2KCl 1 3O2; decomposition
(e)
Ca(NO3)2 1 2HBr → CaBr2 1 2HNO3; double displacement
(f)
Sn(OH)2 → SnO 1 H2O; decomposition
(g)
P4 1 6N2O → P4O6 1 6N2; single displacement
(h)
3Fe 1 Al2(SO4)3 → 3FeSO4 1 2Al single displacement
(i)
2AlCl3 1 3Na2CO3 → Al2(CO3)3 1 6NaCl; double displacement
(j)
2C3H6 1 9O2 → 6CO2 1 6H2O; combustion
Unit C: Chemical Reactions
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8.
The combustion of the fuel for the barbecue will release gases such as carbon dioxide or carbon monoxide
which can be toxic in higher quantities. This means that this sort of cooking should not be done in an
enclosed space.
9. (a)
2N aN3 → 3N2 1 2Na; decomposition
(b)
6Na 1 Fe 2O3 → 3Na2O 1 2Fe; single displacement
(c)
Na2O 1 2CO2 1 H2O → 2NaHCO3; synthesis
SOLVE A PROBLEM
10. (a)
(b)
11. (a)
(b)
12.
ir on 1 oxygen → iron(III) oxide
4Fe 1 3O2 → 2Fe2O3
Students should determine the mass of the sample of steel wool at the beginning of the experiment.
If the reaction does not occur in a closed container, the differences in the mass of the products and the
mass of reactants would be equivalent to the oxygen consumed in the reaction.
2.5 g 1 52.6 g 5 x 1 54.8 g
55.1 g
5 x 1 54.8 g
0.3 g
5x
The results do not appear to follow the law of conservation of mass. However, because the reaction
takes place in an open container, the hydrogen gas is released which accounts for the mass that seems
to be “lost.”
It is best to store gasoline for home use in a cool dark place with the lid firmly on the container. It should
be kept away from flames or heat sources. When using it, open the cap very gently to slowly release
any fumes that may have evaporated during storage because oxygen can break down the gasoline in a
combustion reaction.
CREATE AND EVALUATE
13.
Answers will vary. Sample answer:
(a)
It will be very expensive to provide bottled water to the faculty, staff, and students. This also creates
a tremendous amount of waste which is harmful to the environment and increases the need to have
disposal plans. However, the alternative plan of running the pipes for 20 minutes has many problems
as well. This is a tremendous waste of water and it also only brings the amount of lead in the water to
a “normal” range. This could cause fear and uncertainty with the parents and teachers.
(b)
As a principal, I would provide students and faculty with water bottles that they could keep with them
and provide water for them, in larger dispensers. This would teach responsible use of water and also
keep the waste created to a minimum.
14. (a)
Sample table:
Burning Fossil Fuels
Pros
Cons
current homes and cars built for this use
destroy environment, with drilling and burning
easy to process
very political/dependence on foreign sources
readily available
non-renewable resource
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(b)
Sample answer:
We should keep using fossil fuels because the systems we have in place today work. Much of our
economy focuses on fossil fuels and many profit from it. There are untapped oil reserves in the world
that could meet the current and future demand.
We should not use fossil fuels. Fossil fuels are a non-renewable resource. Once we use them, they are
gone forever. Drilling, processing, and burning fossil fuels destroys the environment. Our dependence
on foreign oil is creating conflict in the world. There are many types of alternative energy sources that
we should be using instead.
REFLECT ON YOUR LEARNING
15. (a)
(b)
16.
Sample answer: I can see how chemical reactions are involved in every part of my life—from eating
food, to heating my home, to disinfecting a cut, to dealing with a rusty bike chain. Chemical reactions
are a fact of life.
The fire triangle is also known as the combustion triangle. The fire triangle shows the three things needed
for a fire to occur; fuel, oxygen, and heat. This relates to firefighting in that if one of these variables is
removed, then the fire will be extinguished. Without oxygen, a fire will die out. Without fuel or heat, the
same thing will happen.
17. (a)
(b)
18. (a)
406
Sample answer: I didn’t think about chemical reactions in my life very much.
The impure reaction is a synthesis reaction; the pure reaction is a decomposition reaction.
Nickel carbonyl is very volatile at room temperature and has been called “liquid death” as a result. It
can be fatal if absorbed through the skin or inhaled. Great care needs to be taken with this substance.
Carbon monoxide is also fatal if exposure is long term. This is why reactions with these substances
need to be conducted in air tight chambers—the gases are too hazardous to humans.
ammonium nitrate → dinitrogen monoxide 1 water
NH4NO3 (s) → N2O 1 2H2O
(b)
This is a decomposition reaction.
(c)
Sample answer: Nitrous oxide is used in the engines of race cars to allow the engine to burn more fuel
and air. This will result in more powerful combustion and more speed.
Unit C: Chemical Reactions
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