Which statements explain why a catalyst is used in the Contact process (shown below)?

\[{\text{S}}{{\text{O}}_2}{\text{(g)}} + \frac{1}{2}{{\text{O}}_2}{\text{(g)}} \rightleftharpoons {\text{S}}{{\text{O}}_3}{\text{(g)}}\]

I.     A catalyst lowers the activation energy.

II.     A catalyst moves the position of equilibrium towards the product.

III.     A catalyst allows the same rate to be achieved at a lower temperature.

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

B

There were a number of comments suggesting that the sentence “A catalyst creates a new reaction pathway of lower activation energy.” should have been used. The examiners accept the rebuke. Nevertheless, nearly 85% of the candidates saw past the poor wording and gave B as the correct answer.