Question

Use each equation to predict whether the relative entropy change is S(products) > S(reactants) or S(products) < S(reactants) and whether ΔS > 0 or ΔS < 0 for the chemical reaction represented. Justify your answer in each case.
a. 2NH3(g)→N2(g) + 3H2(g)
b. 2Al(s) + 3F2(g)→2AlF3(s)

Answer 1

For reaction a, the mole number of gas increase from 2 to 4. So the entropy will increase, ΔS>0. For b, the gas will change to solid, so the entropy decrease, ΔS<0.