The entropy change involved in the isothermal reversible expansion of 2 moles of an ideal gas from a volume of 10 dm3 at 27°C is to a volume of 100 dm3

$∆s=nR\ln \frac{v2}{v1}$ 

$=2.303 nR \log \frac{v2}{v1}$ = $2.303\times 2\times 8.314\times \log \frac{100}{10}$ =  $38.3 J$  $mol-1$ $k-1$