Question

What is the entropy change (∆S) for the following reaction?2H2(g) + O2(g) → 2H2O(l)Given that the standard molar entropy of H2(g), O2(g), and H2O(l) are 131.3 J/K•mol, 205.0 J/K•mol, and 70.0 J/K•mol respectively.

Answer 1

To calculate the entropy change  S  for the reaction, we can use the formula:S = S_products - S_reactantsFor the reactants, we have 2 moles of H2 g  and 1 mole of O2 g . For the products, we have 2 moles of H2O l . We can plug in the given standard molar entropy values:S = [ 2 moles  70.0 J/Kmol H2O l  ] - [ 2 moles  131.3 J/Kmol H2 g   +  1 mole  205.0 J/Kmol O2 g  ]S = [ 140.0 J/K ] - [ 262.6 J/K  +  205.0 J/K ]S = 140.0 J/K - 467.6 J/KS = -327.6 J/KThe entropy change  S  for the reaction is -327.6 J/K.