Reactive Metals Such as Iron Will Reduce Arsenic Acid (H₃AsO₄)

Multiple Choice

Reactive metals such as iron will reduce arsenic acid (H₃AsO₄) to the highly poisonous arsine gas (AsH₃) in the presence of acid. What mass of iron would be required for such a reaction with 250 mL of 0.90 M arsenic acid, assuming that the iron is oxidized to Fe³⁺? 3 H₃AsO₄ + 8 Fe + 24 H⁺ → 3 AsH₃ + 12 H₂O + 8 Fe³⁺

A) 45 g
B) 38 g
C) 34 g
D) 21 g
E) 13 g