Question

What is the change in entropy for the reaction 2H2(g) + O2(g) → 2H2O(g) at a temperature of 298 K?Given the standard entropy values of H2(g), O2(g), and H2O(g) are 130.6 J/K/mol, 205.0 J/K/mol, and 188.7 J/K/mol respectively.

Answer 1

To calculate the change in entropy  S  for the reaction, we can use the formula:S = nS products  - nS reactants where n is the stoichiometric coefficient and S is the standard entropy value for each species.For the reaction 2H2 g  + O2 g   2H2O g , the entropy change is:S = [2  S H2O ] - [2  S H2  + S O2 ]Using the given standard entropy values:S = [2  188.7 J/K/mol] - [ 2  130.6 J/K/mol  + 205.0 J/K/mol]S = [377.4 J/K/mol] - [466.2 J/K/mol]S = -88.8 J/K/molThe change in entropy for the reaction is -88.8 J/K/mol.