Question

$P-V$ plots for two gases during an adiabatic processes are shown in the figure. Plots $1$ and $2$ should correspond respectively to

• A. $He$ and $O_2$
• B. $O_2$ and $He$
• C. $He$ and $Ar$
• D. $O_2$ and $N_2$

Answer 1

The correct option is B $O_2$ and $He$

For an adiabatic process,
$P{V}^{\gamma }=\text{constant}$
For monatomic gas, $\gamma =\frac{C_P}{C_V}=1.67$
For diatomic gas, $\gamma =1.4$
$\Rightarrow {\gamma }_{\text{diatomic}}<{\gamma }_{\text{monatomic}}$
Since slope of adiabatic curve, $\frac{dP}{dV}=-\gamma \frac{P}{V}$
Thus slope of monoatomic will be more than diatomic gas,
Hence, curve $1$ represents graph for diatomic gas and curve $2$ represents graph for a monomatomic gas
$\therefore$Correct option is $\left(b\right)$