Chemical Equilibrium

40% of HI undergoes decomposition to H₂ and I₂ at 300 K. \(\Delta\)G\(^\Theta\) 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)