Question
The molar specific heats of an ideal gas at constant pressure and volume are denoted by $${C_p}$$ and $${C_V}$$ respectively. If $$\gamma = \frac{{{C_p}}}{{{C_V}}}$$ and $$R$$ is the universal gas constant, then $${C_V}$$ is equal to
A.
$$\frac{{1 + \gamma }}{{1 - \gamma }}$$
B.
$$\frac{R}{{\left( {\gamma - 1} \right)}}$$
C.
$$\frac{{\left( {\gamma - 1} \right)}}{R}$$
D.
$$\gamma R$$
Answer :
$$\frac{R}{{\left( {\gamma - 1} \right)}}$$
Solution :
As we know that $${C_p} - {C_V} = R$$
$$\eqalign{
& {C_p} = R + {C_V} \cr
& {\text{and}}\,\,\frac{{{C_p}}}{{{C_V}}} = \gamma \,\,\left( {{\text{given}}} \right) \cr
& {\text{So,}}\,\,\frac{{R + {C_V}}}{{{C_V}}} = \gamma \cr
& \Rightarrow \gamma {C_V} = R + {C_V} \cr
& \Rightarrow \gamma {C_V} - {C_V} = R \cr
& \Rightarrow {C_V} = \frac{R}{{\gamma - 1}} \cr} $$