JAMB Chemistry 2015 Paper

Concept:Use percentage composition to determine the mole ratio, find the empirical formula, then use the molar mass to get the molecular formula.Explanation:Assume $100$ g of the compound.Moles of C = $\frac{40.0}{12} = 3.33$Moles of H = $\frac{6.7}{1} = 6.7$Moles of O = $\frac{53.3}{16} = 3.33$Divide each mole value by the smallest value, $3.33$C: $\frac{3.33}{3.33} = 1$H: $\frac{6.7}{3.33} \approx 2$O: $\frac{3.33}{3.33} = 1$Empirical formula = $\mathrm{CH_2O}$Empirical formula mass = $12 + 2(1) + 16 = 30$$n = \frac{180}{30} = 6$Molecular formula = $(\mathrm{CH_2O})_6 = \mathrm{C_6H_{12}O_6}$Answer:$\mathrm{C_6H_{12}O_6}$ (Option C)