Chapter 18, Problem 94SCQ

For each of the following processes, predict the algebraic sign of Δ_rH°, Δ_rS°, and Δ_rG°. No calculations are necessary; use your common sense.

1. (a) The decomposition of liquid water to give gaseous oxygen and hydrogen, a process that requires a considerable amount of energy.
2. (b) Dynamite is a mixture of nitroglycerin, C₃H₅N₃O₉, and diatomaceous earth. The explosive decomposition of nitroglycerin gives gaseous products such as water, CO₂, and others; much heat is evolved.
3. (c) The combustion of gasoline in the engine of your car, as exemplified by the combustion of octane.

2 C₈H₁₈(g) + 25 O₂(g) → 16 CO₂(g) + 18 H₂O(g)