Question

Determine the entropy change for the combustion of methane gas (CH4) at constant pressure and 298 K. Given the standard molar entropy values are: S°(CH4) = 186 J/mol.K, S°(O2) = 205 J/mol.K, S°(CO2) = 214 J/mol.K and S°(H2O) = 188 J/mol.K.

Answer 1

To determine the entropy change for the combustion of methane gas, we first need to write the balanced chemical equation for the combustion reaction:CH g  + 2O g   CO g  + 2HO g Now, we can calculate the entropy change  S  using the standard molar entropy values provided:S = S products  - S reactants S = [1 mol CO  S CO  + 2 mol HO  S HO ] - [1 mol CH  S CH  + 2 mol O  S O ]S = [1 mol  214 J/mol.K + 2 mol  188 J/mol.K] - [1 mol  186 J/mol.K + 2 mol  205 J/mol.K]S = [214 J + 376 J] - [186 J + 410 J]S = 590 J - 596 JS = -6 J/mol.KThe entropy change for the combustion of methane gas at constant pressure and 298 K is -6 J/mol.K.