Explanations
1. D
If you don’t know which is the incorrect answer here,
at least try to eliminate choices that you know are true. Choice A is
true. Chemical reactions are taking place in the atmosphere. For
example, water freezes to form snow. Choice B is also
a true statement. Clouds form when water vapor collects on a dust
particle. Choice C: you know that oxygen and nitrogen are
major components of the atmosphere, and argon is the next most abundant.
Choice D must be false because it states that the concentration
of carbon dioxide is basically the same everywhere on the planet!
If you live in New York City, the concentration of CO2 in
your neighborhood is definitely higher than in the neighborhood
of someone who lives in rural Kansas. Choice E is true.
The United States and many other countries have desert climates as
well as rainy ones.
2. T, F
(Do not fill in CE.) First look at statement
I—the first step in processing petroleum is to separate its components
based on their different boiling points. For instance, gasoline
is one of the components and can be separated out in this way. This
statement is true. Now look at the second statement. If petroleum
were made up of hydrocarbon chains that had the same number of carbons
in them, we would not be able to separate out the components based
on their boiling points since they would all have the same boiling
point. So this second statement is false, and you would not fill
in the CE oval.
3. B
Choice B, steel, is actually composed of iron and varying
combinations of carbon. All of the rest of the alloys are listed
next to the correct components.
4. E
You should always think about intermolecular forces
in your head when you see the term boiling point.
In order to boil, molecules must separate from each other, and this
takes energy. The molecules that are held most tightly to each other
would require the most energy. Since all the molecules listed are
nonpolar, the determining factor is polarizability—the more electrons
available to have London dispersion forces of attraction. The largest
molecule, hexane, choice E, will have the greatest
attractive forces.
5. D
When excess oxygen is present, combustion will occur.
Hydrocarbon combustion produces carbon dioxide and water. Choice B shows
possible products for an incomplete combustion.
6. A
This question requires you to know the properties of
the various gases listed. Hydrogen, choice A, is odorless,
is colorless, and readily ignites with a popping noise. This is
the answer. Oxygen, choice B, is also odorless, colorless,
and flammable but does not produce any sound when ignited. Carbon
dioxide, choice C, would not ignite. It would put out
a flame. Chlorine, choice D, is a yellow-green gas
that has a pungent odor. It does not readily ignite with a noise.
Choice E might be familiar to you as a gas that you
use in the laboratory. Though methane is flammable, it does not
make a particular sound when ignited.
7. E
This is simply a recall question. The ozone layer in
the atmosphere protects us from UV rays. The other four gases listed
in this question do cause air pollution. CFCs, choice C,
are thought to contribute to the depletion of the ozone layer. Choices A and B are
some of the “greenhouse” gases, especially B, carbon
dioxide. Carbon dioxide is thought to be the reason for global warming.
Choice D is one of the gases that contributes to the
acid rain problem when the gas is released into the atmosphere.
8. A
A hydroxyl group is OH, an amine is the NH2 group
attached to a carbon chain, and carboxylic acids contain the COOH
group. Choice B is methanol, wood alcohol, and does have
the hydroxyl group. Choice C is clearly an amine. Choice D and E are
both carboxylic acids since they contain -COOH. Choice A is
acetic acid, vinegar, and should be placed with the carboxylic acid
group.
