KVPY SA Exam 2016 Question Paper

A 1.85 g sample of an arsenic-containing pesticide was chemically converted to ${\mathrm{AsO}}_4^{3\mathit{–}}$ (atomic mass of As = 74.9) and titrated with ${\mathrm{Pb}}^{2+}$ to form ${\mathrm{Pb}}_3$ ${\left({\mathrm{AsO}}_4\right)}_2$. If 20 mL of 0.1 M ${\mathrm{Pb}}^{2+}$ is required to reach the equivalence point, the mass percentages of arsenic in the pesticide sample is closest to