Calculating S for Reduction

Question

Calculate ∆So for the reduction of aluminum oxide by hydrogen gas:

Al2O3 (s) + 3H2 (g) →2Al (s) + 3H2O (g)

using the following standard entropy values:

Substance So (J/K mol)

Al2O3 (s) 51

H2 (g) 131

Al (s) 28

H2O (g) 189

Answer 1

∑_products - ∑_reactants = ∆S_reaction

∑_products = 2*28 + 3*189 = 623 J/K mol

∑_reactants = 51 + 3*131 = 444 J/K mol

∆S = 623 - 444 = 179 J/K mol