Question

$2$ moles of oxygen are mixed adiabatically with another $2$ moles of oxygen in a mixing chamber, so that the final total pressure and temperature of the mixtures become same as those of the individual constituents at their initial states. The universal gas constant is given as $R$. The change in entropy due to mixing, per mole of oxygen, is given by

• A. $-RIn2$
• B. $-RIn4$
• C. $-RIn2$
• D. $0$

Answer 1

The correct option is D $0$

$dS=m{c}_{v}In\frac{T_2}{T_1}-mRIn\frac{P_1}{P_2}$
Since $P_1=P_2$ and $T_2=T_1$
$\therefore dS=0$