Physics (12th Grade)
posted by Tulika .
When an ideal diatomic gas is heated at constant pressure then what fraction of heat given is used to increase internal energy of gas?

If it is heated at constant pressure, the volume must increase
heat in = change in internal energy + work out
dQ = dU + dW
P V = n R T
constant pressure
P dV = n R dT = work out
Change in internal energy = n Cv dT = n(5/2)R dT for diatomic gas
total heat required = n R dT + (5/2)n R dT
so our answer is (5/2) / (1+5/2)
= 5/(2+5) = 5/7