CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
Consider the gas-phase equilibrium reaction
A2(g)+B2(g)⇌2AB(g),
which has an equilibrium constant Kc=4.0 at a particular temperature.
Answer the following questions qualitatively—no numerical calculation is required.
(a) Describe how the numerical value of the equilibrium constant will change, if at all, when the reaction is written in the reverse direction.
(b) Describe how the numerical value of the equilibrium constant will change, if at all, when the stoichiometric coefficients in the balanced equation are doubled.
(c) Describe how the numerical value of the equilibrium constant will change, if at all, when the reaction is both reversed and its stoichiometric coefficients are doubled in a single step.
(d) For each of the three manipulations in parts (a)–(c), state whether the sign of ΔG∘ for the manipulated reaction becomes positive, negative, or remains zero compared with the sign of ΔG∘ for the original reaction. Justify each answer in terms of the relationship between K and ΔG∘.