WAEC Chemistry 2016 Paper

Concept:When the same two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other are in simple whole-number ratios.Explanation:Element $\mathrm{X}$ forms three different oxides: $\mathrm{X_2O}$, $\mathrm{XO}$, and $\mathrm{XO_2}$.Keeping the mass of $\mathrm{X}$ fixed, compare the masses of oxygen that combine with one atom of $\mathrm{X}$.In $\mathrm{X_2O}$, oxygen per $\mathrm{X}$ atom is $0.5$; in $\mathrm{XO}$, it is $1$; and in $\mathrm{XO_2}$, it is $2$.These oxygen masses are in the ratio $0.5 : 1 : 2$, which simplifies to $1 : 2 : 4$.This is a simple whole-number ratio between the masses of oxygen combined with a fixed mass of $\mathrm{X}$.Therefore, this phenomenon illustrates the law of multiple proportions.Answer:D. Multiple proportion