(A) The amount of potassium chlorate, KClO₃, in a 0.1432 g sample was determined as follows. The sample was dissolved in 50.00 mL of 0.09101 M Fe(NO₃)₂ and the solution was acidified. The excess Fe²⁺ was back-titrated with 12.59 mL of 0.08362 M Ce(NO₃)₄ solution. What is the percentage by mass of KClO₃ in the sample? Chemical equations for the reactions involved are given below.

ClO₃^-(aq) + Fe²⁺(aq) → Cl^-(aq) + Fe³⁺(aq)     (not balanced)

    Fe²⁺(aq) + Ce⁴⁺(aq) → Fe³⁺(aq) + Ce³⁺(aq)

(B) The amount of arsenic, As, in a 7.25 g sample was determined by converting all the arsenic to arsenous acid (H₃AsO₃), and then titrating H₃AsO₃ with 23.77 mL of 0.02144 M KMnO₄. What is the percentage by mass of As in the sample? An unbalanced expression for the titration reaction is H₃AsO₃(aq) + MnO₄^-(aq) → H₃AsO₄(aq) + Mn²⁺(aq).