WAEC Chemistry 2021 Paper

Concept:The relative molecular mass is found by adding the atomic masses of all atoms in the molecular formula.Explanation:The compound shown is methyl benzoate, with molecular formula $\mathrm{C}_6\mathrm{H}_5\mathrm{COOCH}_3$.In condensed form, this contains $8$ carbon atoms, $8$ hydrogen atoms, and $2$ oxygen atoms.Atomic masses: $C = 12$, $H = 1$, $O = 16$.So, relative molecular mass $= (8 \times 12) + (8 \times 1) + (2 \times 16)$.This equals $96 + 8 + 32 = 136$.Answer:Relative molecular mass $= 136$.Correct option: B.