We’re being asked to predict the sign of the entropy change (ΔS) for the given reactions.
Recall that if:
• ΔS > 0 or ΔS = (+); entropy is increased
• ΔS < 0 or ΔS = (–); entropy is decreased
Remember that phase changes lead to a change in entropy:
Also, recall that an increase in the number of gas molecules in the reaction also leads to an increase in entropy.
Predict the sign of the entropy change of the system for each of the following reactions.
(a) N2 (g) + 3H2 (g) → 2NH3 (g)
(b) CaCO3(s) → CaO(s) + CO2(g)
(c) 3C2H2(g) → C6H6(g)
(d) Al2O3(s) + 3H2 (g) → 2Al(s) + 3H2O(g)