Question

Standard entropy of X2, Y2 and XY3 are 60, 40 and 50 JK–1mol–1, respectively. For the reaction, $\frac{1}{2}$X2 +$\frac{3}{2}$ Y2$\rightarrow$ XY3$\Delta$H = – 30 kJ. To be at equilibrium the temperature will be :

• A. 500 K
• B. 750 K
• C. 1000 K
• D. 1250 K

Answer 1

Answer: (B)

750 K

Answer 2

$\Delta$S⁰ reaction = 50 – $\frac{1}{2}$ (60) – $\frac{3}{2}$ (40) = –40 JK–1

For reaction to be at equilibrium

$\Delta$G = 0

$\Delta$H – T$\Delta$S = 0 $\Rightarrow$ T = $\frac{\Delta H}{\Delta S}$ =$\frac{30000}{40}$= 750 K