Two independent equilibria occur simultaneously in a reaction vessel at 298 K:
Reaction I G(g) ⇌ H(g) ΔG°₁ = +0.8 kJ mol⁻¹
Reaction II H(g) ⇌ J(g) ΔG°₂ = −9.0 kJ mol⁻¹
Assume that no other processes affect these species and that ΔG° values are additive for sequential reactions. The thermal energy term RT at 298 K may be taken as 2.5 kJ mol⁻¹. No calculator is to be used.
(1) Without performing an exact calculation, classify each individual reaction (I and II) as product-favored, reactant-favored, or roughly balanced at equilibrium, and justify each classification.
(2) Write the overall balanced chemical equation obtained when Reaction I and Reaction II are combined, and calculate the overall ΔG° for the combined process.
(3) Estimate the equilibrium constant for the overall process to one order of magnitude by chaining together appropriate reasoning steps. Show your entire logical progression without using a calculator.
(4) Explain why a direct, highly accurate numerical evaluation of K is unnecessary for deciding which species (G, H, or J) will dominate the final equilibrium mixture, and state which species will be most abundant.