Question

40% of HI undergoes decomposition to H2 and I2 at 300 K. ΔG° for this decomposition reaction at one atmosphere pressure is _____ J mol-1. [nearest integer]
(Use R = 8.31 J K-1 mol-1; log 2 = 0.3010, ln 10 = 2.3, log 3 = 0.477)

Answer 1

The correct answer is 2735
$HI ⇄ \frac{1}{2} H_2 + \frac{1}{2} l_2$
$1$ $0$ $0$
$1 - α$ $α / 2$ $α / 2$
$ΔG° = - RTInΚ$
$= - RTIn \frac{( ( \frac{α}{2} )^{1 / 2} ( \frac{α}{2})^{1 / 2} ) }{1 - α }$
$= RTIn \frac{α}{2(1 - α )}$
( $α$ = 0.4 )
$= - 8.314 × 300In \frac{0.4}{2 × 0.6 }$
$= + 8.314 × 300 In3$
$= 2735 J / mol$