It was found that the decomposition of ammonium chloride (NH4Cl)
as indicated by the following chemical reaction equation, has an
entropy change for the reaction of 285 J/K, and the enthalpy change
of the reaction was 177 kJ. Given this information, calculate the
Gibbs free energy change (in kJ) for this reaction at 900 K. (4
marks) NH4Cl(s) → NH3(g) + HCl(g)