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

a. S>0 (Because Ammonia is stable at ordinary temperature.
b.S<0(means heat is evolved) Because Fluorine is readily reactive!

Answer 2

For a. the entropy change ΔS>0 due to the S(products)>S(reactants) As it can be seen 2 moles of gas are being converted to 4 moles of gas which is an increase in ΔS. For b. ΔS<0 due to S(products)<S(reactants) it can be seen that 3 moles of gas and 2 moles of solid are being converted to only 2 moles of solid a large entropy decrease.

Answer 3

thanks @Ehsan18 @sweetburger