Cracking the SAT Chemistry Subject Test

Making Gases Even Simpler: The Ideal Gas Equation

The relationship among pressure, volume, amount (moles), and temperature of
an ideal gas is given by the ideal gas equation, PV = nRT

PV  =   nRT

P                       =pressure   in  atm (or mmHg    or  torr)

V                       =volume in  liters

n                       =number of  moles   of  gas particles   in  the container

R                       =the    ideal   gas constant

T                       =temperature    in  Kelvin

On this exam, the ideal gas equation is practically all you need to answer
questions about gases. Let’s start by talking about R—the ideal gas constant,

which is equal to 0.082 (you don’t have to remember that
number for the test).

From looking at the equation, you can see that P is inversely proportional to V.
Both P and V are directly proportional to T and to n. Here’s another way to look
at it. When you think about the ideal gas equation, think

•           Values  on  the same    side    of  the equation    are inversely   proportional    to

each    other   when    the other   variables   are held    constant.