Question

$P-V$ plots for two gases during adiabatic expansion are shown in figure. Plots 1 and plots 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 adiabatic process,$P{V}^{\gamma }$=constant

$\frac{dP}{dV}=-\gamma \frac{P}{V}$

From graph, slope (2) > slope(1)

${\gamma }_2>{\gamma }_1$

We know for mono-atomic gas, $\gamma =1.67$

For diatomic gas $\gamma =1.4$

'2' must be mono-atomic ($He$) and '1' must be diatomic ($O_2$)