Question

$1$ mole of gas occupying $3L$ volume is expanded against a constant external pressure of $1atm$ to a volume of $15L$. The work done by a system is equal to:

• A. $-1.215\times {10}^{3}J$
• B. $-12.15\times {10}^{3}J$
• C. $+1.215\times {10}^{3}J$
• D. $+12.15\times {10}^{3}J$

Answer 1

The correct option is A $-1.215\times {10}^{3}J$

$p_{ext}=1atm$

$V_1=3L\Rightarrow V_2=15L$

As work is done against constant external pressure, the process is irreversible.

$W=-p_{ext}\Delta V$

$=-1atm[15-3]L=-12atmL$

$=-12\times 101.3J[1Latm=101.3J]$

$=-1215.6J=-1.2156\times {10}^{3}J$.

Hence, the correct option is $\text{A}$