Question

p-V plots for two gases during 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

Answer: (B)

$O_2$and He

Answer 2

In adiabatic process
slope of p-V graph $\frac{dp}{dV}=-\gamma \frac{p}{V}$
\hspace20mm slope \gamma \, \, \, \, \, \, (with negative sign)
From the given graph,
\hspace20mm (slope)_2 > (slope)_1
$\therefore \, \, \, \, \, \, \, \, \, \, \, \gamma_2 > \gamma_1$
Therefore, 1 should correspond to $O_2(\gamma = 1.4)$ and 2 should correspond to He ($\gamma$ = 1.67).