Question

Titration with solutions of potassium bromate, KBrO3, can be used to determine the concentration of As(III).

What is the molar concentration of As(III) in a solution if 27.35 mL of 0.100 M KBrO3 is needed to titrate 52.60 mL of the As(III) solution? The balanced equation is
3H₃AsO₃(aq)+BrO₃⁻(aq)→Br⁻(aq)+3H₃AsO₄(aq)

As(III)= ________ M

Answer 1

no. of mole = Molarity volume of solution in liter

27.35 ml = 0.02735 liter

no. of mole of KBrO₃ = 0.100 0.02735 = 0.002735 mole

According to reaction for 1 mole of BrO₃ required 3 mole of H₃AsO₃ for complete reaction then for to react with 0.002735 mole of BrO₃ requied mole of H₃AsO₃ = 0.002735 3 = 0.008205 mole

mole of H₃AsO₃ = 0.008205 mole

volume of H₃AsO₃ = 52.60 ml = 0.05260 liter

Molarity = no. of mole / volume of solution in liter

Molarity of H₃AsO₃  = 0.008205 / 0.05260 = 0.156 M

molar concentration of As(lll) = 0.156 M