Molar specific heat capacities for gases

[saubhik]

For an isochoric process,
dV = 0
therefore dW=0
So from 1st of Thermodynamics,
dQ = dU + 0
or, n*Cp*dT = n*Cv*dT (Cp and Cv denote molar heat capacities of the gas at const pressure and volume resp.)

therefore we get Cp = Cv .(how can this be possible once we know Cp - Cv = R ?)

[rock.freak667]

If you are heating at constant volume, how does dQ=ncpdT?

If dQ=dU

and dU/dT = cv, then you'll just get Q= ncvΔT