Question

Arsenic acid (35.5 g) is react with excess of H₂S in presence of conc. HCl to give Arsenic pentasulphide.What will be amount formed of Arsenic pentasulphide?

Answer 1

Dear Student,

$$\begin{gathered} 2{\mathrm{H}}_3{\mathrm{AsO}}_4+5{\mathrm{H}}_2\mathrm{S}\to {\mathrm{As}}_2{\mathrm{S}}_5+8{\mathrm{H}}_2\mathrm{O} \\ \mathrm{Now},2\mathrm{moles}\mathrm{of}\mathrm{arsenic}\mathrm{acid}\mathrm{reacts}\mathrm{with}{\mathrm{H}}_2\mathrm{S}\mathrm{to}\mathrm{form}1\mathrm{mole}\mathrm{of}\mathrm{Arsenic}\mathrm{pentasulphide} \\ \mathrm{i}.\mathrm{e}.2\times 142\mathrm{g}\mathrm{of}\mathrm{Arsenic}\mathrm{acid}\mathrm{reacts}\mathrm{to}\mathrm{give}310\mathrm{g}\mathrm{of}\mathrm{arsenic}\mathrm{pentasulphide} \\ \mathrm{So},35.5\mathrm{g}\mathrm{of}\mathrm{Arsenic}\mathrm{acid}\mathrm{will}\mathrm{give}\frac{310}{284}\times 35.5=38.75\mathrm{g} \end{gathered}$$