Predict the sign of ΔS for the following reactions. Then predict whether the reaction is spontaneous, non-spontaneous, or dependent on the magnitude of ΔH, ΔS and temperature.

Question

a.) Na2CO3 (s) Na2O (s) + CO2 (g) (endothermic)

b.) 2NF3 (l) N2 (g) + 3F2(g) (exothermic)

c.) 2XeO3 (s) 2Xe (g) + 3O2(g) (exothermic)

Answer 1

a. ΔH is positive and ΔS is positive (production of a gas), so ΔG is temperature dependent.

b. ΔH is negative and ΔS is positive, so ΔG will be negative (spontaneous).

c. ΔH is negative and ΔS is positive, ΔG will be negative (spontaneous).