Question

Calculate the entropy change (ΔS) for the reaction below at 298 K:2H2(g) + O2(g) → 2H2O(l)Given the standard molar entropy values are:H2(g) = 130.68 J/K molO2(g) = 205.03 J/K molH2O(l) = 69.91 J/K mol

Answer 1

To calculate the entropy change  S  for the reaction, we need to find the difference between the entropy of the products and the entropy of the reactants. The equation for this is:S = nS products  - nS reactants where n is the stoichiometric coefficient and S is the standard molar entropy.For the given reaction:S = [2  S H2O l  ] - [2  S H2 g   + S O2 g  ]Now, we can plug in the given standard molar entropy values:S = [2  69.91 J/K mol] - [2  130.68 J/K mol + 205.03 J/K mol]S = [139.82 J/K mol] - [261.36 J/K mol + 205.03 J/K mol]S = 139.82 J/K mol - 466.39 J/K molS = -326.57 J/K molThe entropy change  S  for the reaction is -326.57 J/K mol.