Question

What is the value for

º

for the following reaction, given the standard entropy values?


Al2O3(s) + 3H2(g) → 2Al(s) + 3H2O(g)



–35 J/mol·K




+35 J/mol·/K




+179 J/mol·K




–179 J/mol·K

Answer 1

179 (J/K*mol)

Step-by-step 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)