Question

$1g{H}_2$ gas expand at STP to occupy double of its original volume. The work done during the process is:

• A. 260 cal
• B. 180 cal
• C. 130 cal
• D. 270 cal

Answer 1

Answer: (D)

270 cal

Solution:- (D) $270\text{cal}$

At STP, temperature is $273K$.

As we know that,

No. of moles $\left(n\right)=\frac{\text{wt.}}{\text{Mol. wt.}}$

Given weight $=1g$

Mol. wt. $=2g$

$\therefore n=\frac{1}{2}=0.5\text{mole}$

$R=2cal/mol-K$

$W=P\Delta V=nRT$

$W=0.5\times 2\times 273=273\text{cal}\approx 270\text{cal}$

Hence the work done will be $270\text{cal}$.

As both, temperature and pressure are constant. Hence, we cannot conclude that the process is isothermal or isobaric.