Question
Fri March 21, 2014 By: Arjun Kharbanda

what is Mayer's formula

Expert Reply
Fri March 21, 2014

Mayer 's formula gives the relationship between molar specific heat of a gas at constant volume and pressure.

By using 1st law of thermodynamics,

dQ=dU + pdv

If specific heat of a gas at constant volume

Cv = (dQ / dT)v

Cv = dU / dT ...................(1st)

If specific heat capacity at constant pressure

Cp = (dQ / dT)p

Cp = dU + Pdv / dT

Cp = dU / dT + P(dV / dT)

Cp = Cv + Pdv / dT (using 1st) ........................(2)

By applying ideal gas equation for 1 mole

PV = nRT

PV = (1)RT

PV = RT

P dv / dt = R dT / dt

Pdv = RdT

P(dv / dT) =R

Putting dis value in eqn 2nd we get,

Cp - Cv = R   [Mayer's relation]

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