Answer:
179 (J/K*mol)
Explanation:
The value for ΔSºreaction for this reaction is calculated as follows:
2 * Sº of Al(s) + 3 * Sº of H2O(g) - 3 * Sº of H2(g) - S° of Al2O3(s)
that is, the subtraction of the standard entropy of the reactants to the products.
| Al(s) | H2O(g) | H2(g) | Al2O3(s)
standard entropy (J/K*mol) | 28.3 | 188.825 | 130.684 | 50.92
So:
ΔSºreaction = 2*28.3 + 3*188.825 - 3*130.684 - 50.92 ≈ 179 (J/K*mol)