To calculate the change in entropy for this reaction, we need to find the difference between the entropy of the products and the entropy of the reactants. The reaction is:2 H g + O g 2 HO g First, we need to find the standard molar entropies S for each substance involved in the reaction. The standard molar entropies at 298 K are:S H = 130.6 J/molKS O = 205.1 J/molKS HO = 188.8 J/molKNow, we can calculate the change in entropy S for the reaction:S = [2 S HO ] - [2 S H + S O ]S = [2 188.8 J/molK] - [2 130.6 J/molK + 205.1 J/molK]S = [377.6 J/molK] - [466.3 J/molK]S = -88.7 J/molKThe change in entropy for this reaction is -88.7 J/molK.