Consider the following reaction:

${\text{2A}} \rightleftharpoons {\text{C}}$     ${K_{\text{c}}} = 1.1$

Which statement is correct when the reaction is at equilibrium?

A.     ${\text{[A]}} \gg {\text{[C]}}$

B.     ${\text{[A]}} > {\text{[C]}}$

C.     ${\text{[A]}} = {\text{[C]}}$

D.     ${\text{[A]}} < {\text{[C]}}$

D

One respondent felt that this question required too much mathematical analysis. 61.21% of the candidates, however, gave the correct answer. It is not too much of a step from [C] / ${{\text{[A]}}^{\text{2}}} = 1.1$ (Assessment statement 7.2.1) to realizing that [C] must be larger than [A] – and then there is only one possible answer.