JAMB Chemistry 2024 Paper

Concept:In a combustion equation, atoms are conserved, so the formula of the fuel can be found by balancing the number of atoms of each element.Explanation:The products are $4\mathrm{CO}_2$ and $4\mathrm{H}_2\mathrm{O}$.They contain $4$ carbon atoms and $8$ hydrogen atoms.Total oxygen atoms on the right side $= (4 \times 2) + (4 \times 1) = 12$.The $5\mathrm{O}_2$ molecules supply $10$ oxygen atoms.Therefore, the fuel must contribute $2$ oxygen atoms.This gives the full formula $\mathrm{C}_4\mathrm{H}_8\mathrm{O}_2$.Since $2$ is a common factor of all the subscripts, divide through by $2$.The simplest formula is $\mathrm{C}_2\mathrm{H}_4\mathrm{O}$.Answer:D. $\mathrm{C}_2\mathrm{H}_4\mathrm{O}$