Gases and the Gas Laws

5

These skills are usually tested on the SAT Subject Test in Chemistry. You
should be able to...

Describe the physical and chemical properties of oxygen and

hydrogen and the electronic makeup of their diatomic molecules.

Explain how atmospheric pressure is measured, how to read the

pressure in a manometer, and the units used to measure pressure.

Read and explain a graphic distribution of the number of

molecules versus kinetic energy at different temperatures.

Know and use the following laws to solve gas problems:

Graham’s, Charles’s, Boyle’s, Dalton’s, the Combined Gas Law,

and the Ideal Gas Law.

This chapter will review and strengthen these skills. Be sure to do the
Practice Exercises at the end of the chapter.

When we discuss gases today, the most pressing concern is the gases in our

atmosphere. These are the gases that are held against Earth by the gravitational
field. The principal constituents of the atmosphere of Earth today are nitrogen
(78%) and oxygen (21%). The gases in the remaining 1% are argon (0.9%),
carbon dioxide (0.03%), varying amounts of water vapor, and trace amounts of
hydrogen, ozone, methane, carbon monoxide, helium, neon, krypton, and xenon.
Oxides and other pollutants added to the atmosphere by factories and automobiles
have become a major concern because of their damaging effects in the form of
acid rain. In addition, a strong possibility exists that the steady increase in
atmospheric carbon dioxide, mainly attributed to fossil fuel combustion over the
past century, may affect Earth’s climate by causing a greenhouse effect, resulting
in a steady rise in temperatures worldwide.

TIP

The major components of Earth’s atmosphere:

78% nitrogen