Take a look at the units of R, they tell you what the other
units have to be in. If the units are different, simply
convert it.

A 16.0 g sample of methane gas, CH_{4}, the
gas used in chemistry lab, has a volume of 5.0 L at 27ēC.
Calculate the pressure.

Looking at all the information given, you have a mass,
a volume, and a temperature, and you need to find the
pressure of the system. As always, start by checking
your units. You must first convert 16.0 g of CH_{4}
into moles: 16.0 g CH_{4 }x 1 mol CH_{4}/16.0 g CH_{4} = 1.00
mol of methane. The volume is in the correct units,
but you must convert the temperature into Kelvins: 27
+ 273 = 300.K. Now you’re ready to plug these numbers
into the ideal gas law equation: