Barrons SAT Subject Test Chemistry, 13th Edition

Once R is known, the Ideal Gas Law can be used to find any of the variables,
given the other three.
For example, calculate the pressure, at 16.0°C, of 1.00 gram of hydrogen gas
occupying 2.54 liters.
Rearranging the equation to solve for P, we get

TIP

Remember to use appropriate units:

moles (mol)

liters (L)

atmosphere (atm)

The molar mass of hydrogen is 2.00 g/mol, so the number of moles in this
problem would be

Substituting the known values, we have

Calculating the value, we get

P = 4.66 atm

Another use of the ideal gas law is to find the number of moles of a gas when
P, T, and V are known.
For example, how many moles of nitrogen gas are in 0.38 liter of gas at 0°C
and 0.50 atm pressure?
Rearranging the equation to solve for n gives

Changing temperature to kelvins and pressure to atmospheres gives