Question

A cylinder contains acetylene gas at ${27}^{o}C$ and 4.05 $MPa$. The pressure in the cylinder after half the mass of gas is used up and temperature has fallen to ${12}^{o}C$ will be :

• A. 4.05 $MPa$
• B. 2.025 $MPa$
• C. 3.84 $MPa$
• D. 1.92 $MPa$

Answer 1

The correct option is D 1.92 $MPa$

As we know, $PV=\frac{w}{M_w}RT$

$\frac{P}{wT}=const$
$PV=\frac{P_1}{w_1{T}_1}=\frac{P_2}{w_2{T}_2}$

By putting all the given values, we get

$PV=\frac{4.05}{w\times 300}=\frac{P_2}{\frac{w}{2}\times 285}$

$P_2$ = $1.92$ $MPa$

Hence, the correct option is $D$