Question

The ratio of the specific heats of a gas is $\frac{C_p}{C_v} = 1.66$, then the gas may be

• A. $CO_2$
• B. $He$
• C. $H_2$
• D. $NO_2$

Answer 1

Answer: (B)

$He$

Answer 2

Let '$n$' be the degree of freedom
$\gamma=\frac{C_{p}}{C_{v}}=\frac{\left(\frac{n}{2}+1\right) R}{\left(\frac{n}{2}\right) R}=\left(1+\frac{2}{n}\right)=1.66$
$=\frac{5}{3}=\left(1+\frac{2}{3}\right)$
$\Rightarrow n=3$
$\Rightarrow$ gas must be monoatomic.