5 Steps to a 5 AP Chemistry

CHAPTER

8

102 

KEY IDEA

Gases

IN THIS CHAPTER

Summary:Of the three states of matter—gases, liquids, and solids—gases are

probably the best understood and have the best descriptive model.

While studying gases in this chapter you will consider four main physical

properties—volume, pressure, temperature, and amount—and their inter-

relationships. These relationships, commonly called gas laws, show up quite

often on the AP exam, so you will spend quite a bit of time working problems

in this chapter. But before we start looking at the gas laws, let’s look at the

Kinetic Molecular Theory of Gases, the extremely useful model that scientists

use to represent the gaseous state.

Keywords and Equations

Gas constant, R=0.0821 L atm mol−1K−1

urms=root-mean-square speed

r=rate of effusion

STP=0.000°C and 1.000 atm

PV=nRT

PA=Ptotal×XA, where XA=

Ptotal=PA+PB+PC+...

moles

total moles

A

P na

V

+ Vnb nRT

⎛

⎝

⎜

⎞

⎠

⎟ −=

2

2 ()

r

r

M

M

1

2

2

1

=