# Change in internal energy in air

#### S1CkFiSh

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?

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#### Andrew Mason

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

#### S1CkFiSh

ok, thank you very much its appreciated

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