For a reversible gaseous reaction at constant temperature
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
For a reversible gaseous reaction at constant temperature, imagine that the balanced chemical equation is written in three different ways based on the same chemical system. No numerical values are provided; the emphasis is on qualitative reasoning about the magnitude and algebraic form of the equilibrium constant.
Original form (unmodified):
P(g) → Q(g) with equilibrium constant K1.
Rewrite 1: Q(g) → P(g)
Rewrite 2: 3 P(g) → 3 Q(g)
Rewrite 3: 2 Q(g) → 2 P(g)
Answer the following about the relationship between the equilibrium constants of each rewritten equation and K1. Justify all answers in words and with appropriate symbolic expressions.
(1) Part 1: (a) Describe how the equilibrium constant for Rewrite 1 compares to K1, and explain the chemical reason for this relationship.
(2) Part 2: (b) Determine the algebraic expression for the equilibrium constant of Rewrite 2 in terms of K1, and explain why the numerical value changes in that fashion.
(3) Part 3: (c) Rewrite 3 can be obtained by first reversing the original equation and then multiplying the resulting equation by 2. Derive an expression for the equilibrium constant of Rewrite 3 in terms of K1 and justify each step in your derivation.