Question

The molar specific heat at constant pressure of an ideal gas is $(7/2)R$. The ratio of specific heat at constant pressure to that at constant volume is :-

• A. 9/7
• B. 7/5
• C. 8/7
• D. 5/7

Answer 1

Answer: (B)

Molar specific heat at constant pressure
$C_{P}=\frac{7}{2} R$
Since, $C_{P}-C_{V}=R$
or, $C_{V}=C_{P}-R=\frac{7}{2} R-R=\frac{5}{2} R$
$\therefore \frac{C_{P}}{C_{V}}=\frac{(7 / 2) R}{(5 / 2) R}=\frac{7}{5}$