Lesson: Chapter - 10

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.

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