Question

The value of $\gamma =$ $\frac{C_p}{C_v}$ for hydrogen, helium and another ideal diatomic gas X, are respectively equal to:

• A. $\frac{7}{5},\frac{5}{3},\frac{7}{5}$
• B. $\frac{7}{5},\frac{5}{3},\frac{9}{7}$
• C. $\frac{5}{3},\frac{7}{5},\frac{9}{7}$
• D. $\frac{5}{3},\frac{7}{5},\frac{7}{5}$

Answer 1

The correct option is A $\frac{7}{5},\frac{5}{3},\frac{7}{5}$

$C_p$ value for hydrogen gas is $\frac{7R}{2}$ and $C_v$ value is $\frac{5R}{2}$
So, $\gamma$ = $\frac{C_p}{C_v}$ = $\frac{7}{5}$
which is $\gamma$ for any diatomic gas
$C_p$ value for helium gas is $\frac{5R}{2}$ and $C_v$ value is $\frac{3R}{2}$
So, $\gamma$ = $\frac{C_p}{C_v}$ = $\frac{5}{3}$
which is $\gamma$ for any monoatomic gas.