Question

When gases are allowed to expand suddenly they:

• A. heat up
• B. collapse
• C. react
• D. cool

Answer 1

The correct option is D cool

According to the joule-thomson effect, when a gas is alloowed to expand, under adiatatic conditions, lowering of temperature occurs.

Under adiabatic conditions,

$T(V{)}^{r-1}=constant$

$\therefore T_1{V}_1^{r-1}=T_2{V}_2^{r-1}$

$\therefore T_2=T_1(\frac{V_1}{V_2}{)}^{r-1}$

$r-1>0$ as $r>1,$ Also at expansion $V_2>V_1$.

$\therefore T_2<T_1$ i.e. Cooling occurs.