Q.
The amount of arsenic pentasulphide that can be obtained when 35.5g arsenic acid is treated with excess H2S in the presence of conc. HCl ( assuming 100% conversion) is :
2H3AsO4+5H2S Conc HCl AsS5+8H2O
2 moles of Arsenic Acid ⟶1 mole of Arsenic Pentasulphide
1 moles of Arsenic Acid ⟶1/2 mole of Arsenic Pentasulphide Molar mass of As2S5=308 Molar mass of H3AsO4=141 number of moles of H3AsO4=14135.5=0.25 ∴ number of moles of As2S5=20.25=0.125mol