Question

What are the values of $w$ and $△E$, when a system absorbs $250J$ of heat by expanding from $1$ lit to $10$ lit against $0.5atm$ pressure and at a constant temperature?

Answer 1

As we know that in the expansion of gas, work is done by the system.

$\therefore W=-P_{ext}\Delta V$

Given that:-

$P_{ext.}=0.5atm$

$V_i=1L$

$V_f=10L$

$\therefore W=-0.5(10-1)=-4.5L-atm=-456J$

Given $q=+250J$

Now from first law of thermodynamics,

$\Delta E=q+w=250+(-456)=-206J$

Hence the values of $w$ and $\Delta E$ $-456J$ and $-206J$.