JEE Main · 2021 · 18 Mar 2021 · Shift 2 · Some Basic Concepts of Chemistry

Bromination over iron(III) bromide substitutes one bromine atom on the ring, so one mole of benzoic acid can give at most one mole of m-bromobenzoic acid. The molar masses are $122$ g mol${}^{-1}$ for ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH}$ and $122-1+80=201$ g mol${}^{-1}$ for ${\mathrm{C}}_6{\mathrm{H}}_4\mathrm{BrCOOH}$. The acid taken is $\frac{6.1}{122}=0.05$ mol, so the theoretical mass of product is $0.05\times 201=10.05$ g. The percentage yield is

Rounded to the nearest integer, the percentage yield of m-bromobenzoic acid is $78$.