One mole of a Van der Waals gas which had initially the volume `V_1` and the temperature `T_1` was transferred to the state with the volume `V_2` and the temperature `T_2`. Find the corresponding entropy increment of the gas, assuming its molar heat capacity `C_V` to be known.

Explanation

We use, `Delta S = int_(V_1,T_1)^(T_1,T_2) dS (V,T) = int_(T_1)^(T_2) ((del S)/(del T))_(V_1) dT + int_(V_1)^(V_1) ((del S)/(del V))_(T = T_2) dV `
=`int_(T_1)^(T_2) (C_V dT)/(T) + int_(V_1)^(V_2) (R)/(V - b) dV = C_V 1n (T_2)/(T_1) + R 1n (V_2 - b)/(V_1 - b)`
assuming `C_V, a, b` to be known constant.