For the reaction 2A ⇌ B + C, K_c = 4 ×… | Reaction Quotient (Qc) vs Equilibrium Constant (Kc)

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For the reaction $2A \rightleftharpoons B + C$, $K_c = 4 \times 10^{-3}$. At a given time, the composition of reaction mixture is: $[A] = [B] = [C] = 2 \times 10^{-3}$ M. Then, which of the following is correct?

A Reaction has a tendency to go in backward direction.

B Reaction has gone to completion in forward direction.

C Reaction is at equilibrium.

D Reaction has a tendency to go in forward direction.

The answer is A.

Solution

For $2A \rightleftharpoons B + C$: $Q_c = \frac{[B][C]}{[A]^2}$ $Q_c = \frac{(2 \times 10^{-3})(2 \times 10^{-3})}{(2 \times 10^{-3})^2} = 1$ $K_c = 4 \times 10^{-3}$ (given), so $K_c < Q_c$ Hence the reaction has a tendency to go in the backward direction.

Concept Predicting direction of reaction using Qc and Kc

For the reaction $2A \rightleftharpoons B + C$, $K_c = 4 \times 10^{-3}$. At a given time, the composition of reaction mixture is: $[A] = [B] = [C] = 2 \times 10^{-3}$ M. Then, which of the following is correct?

Solution

Equilibrium in past papers

Practice

Free resources

Platform

At the institute