Which expression gives the sum of all the coefficients for the general equation for the complete

combustion of hydrocarbons?

___ \({{\text{C}}_x}{{\text{H}}_y}{\text{(g)}} + \) ___ \({{\text{O}}_{\text{2}}}{\text{(g)}} \to \) ___ \({\text{C}}{{\text{O}}_{\text{2}}}{\text{(g)}} + \) ___ \({{\text{H}}_{\text{2}}}{\text{O(l)}}\)

A.     \(1 + x + \frac{y}{4}\)

B.     \(1 + x + \frac{y}{2}\)

C.     \(1 + 2x + \frac{{3y}}{4}\)

D.     \(1 + 2x + \frac{{3y}}{2}\)

C

Although this might have seemed unfamiliar, nearly 50% gave the correct answer. Many thought this was too challenging for an early question. The examination questions are, and have been for many years, presented in topic order. Those candidates who find the more mathematical manipulation testing should, perhaps, be advised the tackle the questions in a different order.