Question

Standard entropies of $x_{2},y_{2}$ and $xy_{3}$ are 70, 50 and 60 J $K^{- 1}mol^{- 1}$ respectively. For the reaction $\frac{1}{2}x_{2}+\frac{3}{2}y_{2}\rightleftharpoons xy_{3}.\Delta H=-30kJ$ to be at equilibrium, the temperature should be

• A. 450 K
• B. 600 K
• C. 1200 K
• D. 300 K

Answer 1

Answer: (B)

$\Delta S=S_{x y_{3}}-\frac{1}{2}S_{x_{2}}-\frac{3}{2}S_{y_{2}}$

$\Delta S=60-\frac{1}{2}\times 70-\frac{3}{2}\times 50$

$=-50$ $JK^{- 1} \, mol^{- 1}$

At equilibrium $\Delta G=0$

$\Delta G=\Delta H-T\Delta S$

$0=-30-\left(\right.-50\times 10^{- 3}\times T\left.\right)$

$T=600 \, \text{K}$