Equation for molar specific heat

n_1 moles of a monatomic gas and n_2 moles of a diatomic gas are mixed together in a container. Derive an expression for the molar specific heat at constant volume of the mixture. Expression must be in terms of n_1, n_2, and the gas constant R.

I know that the molar specific heat of the entire mixture is Q = C_v(n_1+n_2)*delta(T). and my physics professor told me that I can use the equation Q = 3/2nR*delta(T) and set it equal to C_v(n_1+n_2)*delta(T) and somehow use that to solve for something, but I'm not sure what I can solve for. I keep getting C_v = 3/2R, but when I plug that in, the equation doesn't work ( 3/2R(n_1+n_2) is incorrect ). I would appreciate some help. Thanks

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 Recognitions: Gold Member Homework Help Science Advisor The molar specific heat of a diatomic gas is 5/2R. Does this help?
 Got it! Thanks!