# Change in internal energy in air

If we apply 300 kJ of heat to 2500 moles of air at constant pressure, what is the change in internal energy?

So far i think I use the equation: (f/x)nkT, but I don't know how to calculate the degrees of freedom and whether I do or not, and whether or not to calculate the number of moles by n=2500/6.022 x 10^23 (avogadro's constant), or if I just plug 2500 moles into n?

## Answers and Replies

Andrew Mason
Science Advisor
Homework Helper
If we apply 300 kJ of heat to 2500 moles of air at constant pressure, what is the change in internal energy?

So far i think I use the equation: (f/x)nkT, but I don't know how to calculate the degrees of freedom and whether I do or not, and whether or not to calculate the number of moles by n=2500/6.022 x 10^23 (avogadro's constant), or if I just plug 2500 moles into n?
Look up the Cp for air. It consists mainly of diatomic molecules (N2, O2), if you want to figure it out.

AM

ok, thank you very much its appreciated