Question

6 g of $O_2$ gas at STP is expanded against atmosphere so that the volume is doubled. Thus, the work done is:

• A. 22.4 L atm
• B. - 4.2 L atm
• C. 5.6 L atm
• D. 11.2 L atm

Answer 1

The correct option is B - 4.2 L atm

Expansion work,
$W=-p_{ext}△V=-P_{ext}(V_{final}-V_{initial})$

At STP we have:
$V=22.4L$
$p_{ext}=1atm$
Moles of $O_2$ $=\frac{6}{32}=0.1875mol$
$V_{intial}=22.4\times 0.1875=4.2L$
$V_{initial}=4.2L$
$V_{final}=2\times 4.2=8.4L$
Thus, $△V=4.2L$
So, $W=-(1atm\times 4.2L)=-4.2Latm$