Question

$3$ moles of ${CO}_2$ gas expands isothermally against external pressure of $1$ bar. Volume increases from $10L$ to $30L$ respectively. The system is in thermal contact of surroundings at temperature $15oC$. Entropy change in isothermal process is:
$\Delta S=2.303nR\log \left(\frac{V_2}{V_1}\right)$
Select the correct relation:

• A. $\Delta S_{system}>0,\Delta S_{surr.}=0$
• B. $\Delta S_{system}<0,\Delta S_{surr.}>0$
• C. $\Delta S_{system}=0,\Delta S_{surr.}=0$
• D. $\Delta S_{system}>0,\Delta S_{surr.}<0$

Answer 1

Answer: (D)

$\Delta S_{system}>0,\Delta S_{surr.}<0$

On expansion of gas from 10 L to 30 L, the entropy of a system increases because the degree of randomization increases,

so, $\Delta S_{system}>0$

and with increase in the entropy of system, the entropy of surrounding decreases

$\Delta S_{surr.}<0$