Question

$1$ mole of gas occupying $3L$ volume is expanded against a constant external pressure of $1$ atm to a volume of $15 \,L$. 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

Answer: (A)

$p_{ ext }=1 \,atm$

$V_{1}=3 L$

$ \Rightarrow \,V_{2}=3 L$

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

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

$=-1 \,atm [15-3] L=-12 \, atm\, L$

$=-12 \times 101.3 \,J [11 \,atm =101.3\, J ]$

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