WAEC Chemistry 2021 Paper

Concept:The empirical formula of a compound is the simplest whole-number ratio of the moles of each element present.Explanation:The hydrocarbon contains $0.160$ moles of carbon and $0.640$ moles of hydrogen.To find the simplest ratio, divide each mole value by the smallest number of moles, which is $0.160$.For carbon: $\frac{0.160}{0.160} = 1$For hydrogen: $\frac{0.640}{0.160} = 4$Therefore, the ratio of carbon to hydrogen is $1 : 4$.Since the compound is a hydrocarbon, it contains only carbon and hydrogen atoms.So the empirical formula is written as $\mathrm{C}_1\mathrm{H}_4$, which is simplified to $\mathrm{CH}_4$.This formula represents the smallest whole-number ratio of atoms in the hydrocarbon.Answer:$\mathrm{CH}_4$