Curve X on the graph below shows the volume of oxygen formed during the catalytic decomposition of a ${\text{1.0 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}$ solution of hydrogen peroxide.

$${\text{2}}{{\text{H}}_2}{{\text{O}}_2}{\text{(aq)}} \to {{\text{O}}_2}{\text{(g)}} + {\text{2}}{{\text{H}}_2}{\text{O(l)}}$$

Which change would produce the curve Y?

A.     Adding water

B.     Adding some 0.1 mol dm–3 hydrogen peroxide solution

C.     Using a different catalyst

D.     Lowering the temperature

B

Two respondents stated that this question was somewhat misleading. The question was one of the more challenging questions on the paper but 51.70% of candidates did get B. as the correct answer.