JAMB Chemistry 2024 Paper

Concept:The empirical formula shows the simplest whole-number ratio of atoms in a compound, which can be found from percentage composition by mass.Explanation:The oxide contains only sulphur and oxygen, so if oxygen is $60\%$, then sulphur must be $40\%$.Convert each percentage to moles by dividing by the corresponding atomic mass:Sulphur: $\frac{40}{32} = 1.25$ moles.Oxygen: $\frac{60}{16} = 3.75$ moles.Divide both values by the smallest mole value $(1.25)$ to get the simplest ratio:Sulphur: $\frac{1.25}{1.25} = 1$.Oxygen: $\frac{3.75}{1.25} = 3$.Thus, the ratio of sulphur to oxygen is $1:3$.This corresponds to the empirical formula $\mathrm{SO}_3$.Answer:A. $\mathrm{SO}_3$