Heat Capacity of Air
Cmolar-constant P = Cmolar-constant V + R
Air is made up mostly of N2 and O2. These gases act approximately as diatomic ideal gases. Usually, when we heat air it is NOT in a contained volume but expands to keep its pressure constant. This means that most of the time, the heat capacity of air is:
Cmolar - air - constant P = (5/2)R + R = (7/2)R .