Question

An open bulb containing air at ${19}^{\circ }C$ was cooled to a certain temperature at which the number of moles of the gaseous molecules increased by $25\%$. The final temperature is:

• A. $-{39.4}^{\circ }C$
• B. ${233.6}^{\circ }C$
• C. ${39.4}^{\circ }C$
• D. ${240}^{\circ }C$

Answer 1

The correct option is A $-{39.4}^{\circ }C$

From the ideal gas relation,

$PV=nRT$

Since the pressure and volume in the given problem is constant, we get

$nT=constant$

$\Rightarrow n_1{T}_1=n_2{T}_2$

$\Rightarrow T_2=\frac{T_1}{1.25}=\frac{292}{1.25}=233.6K=-{39.4}^{o}C$