Question

The change in entropy when 1 mole of $N_2$ gas expands isothermally and reversibly from an initial volume of 1 litre to a final volume of 10 litre at ${27}^{o}C$ is:

• A. $-19.15{JK}^{-1}{mol}^{-1}$
• B. $+19.15{JK}^{-1}{mol}^{-1}$
• C. $+14.19{JK}^{-1}{mol}^{-1}$
• D. $-14.15{JK}^{-1}{mol}^{-1}$

Answer 1

The correct option is B $+19.15{JK}^{-1}{mol}^{-1}$

For an isothermal reversible process, change in entropy for an ideal gas is given by,

$\Delta S=nRln\left(\frac{V_2}{V_1}\right)$

$=1\times 8.314\times ln\left(10\right)$

$\approx 19.15J{K}^{-1}mo{l}^{-1}$

Hence, option B is correct.