1mole of ideal gas at 25°C is subjected to expand reversibly ten times of its initial volume. The change in entropy of expansion is

Expansion takes place at constant temperature so it is isothermal process (w = q)

${\mathrm{\Delta S}}_{\mathrm{sys}}={\mathrm{nC}}_{\mathrm{v}}\ln \frac{{\mathrm{T}}_2}{{\mathrm{T}}_1}+\mathrm{nRln}\frac{{\mathrm{V}}_2}{{\mathrm{V}}_1}$

$\therefore \Delta S=2.303\times 1\times 8.314\times \log \left(\frac{10}{1}\right)$

$=19.15J{K}^{-1}mo{l}^{-1}$