Question

Calculate the standard entropy change for the reaction: 2H2 (g) + O2 (g) -> 2H2O (g) given the standard enthalpy of formation of H2O (g) is -241.8 kJ/mol at 298 K.

Answer 1

To calculate the standard entropy change for the reaction, we need the standard molar entropies of the reactants and products. The standard molar entropies  S  at 298 K are as follows:H2  g : 130.7 J/molKO2  g : 205.2 J/molKH2O  g : 188.8 J/molKNow, we can calculate the standard entropy change  S  for the reaction using the following equation:S =  S products  -  S reactants S = [2  188.8 J/molK] - [2  130.7 J/molK + 205.2 J/molK]S = [377.6 J/molK] - [467.6 J/molK]S = -90 J/molKSo, the standard entropy change for the reaction is -90 J/molK.