Question

Identify the elements undergoing reduction and oxidation respectively in the following redox reaction.

$3H_3AsO_3 + BrO_3 \rightarrow Br + 3H_3AsO_4$

• A. As and O
• B. Br and As
• C. As and Br
• D. Br and O

Answer 1

Answer: (B)

Br and As

Answer 2

1. For Arsenic:

   • In $H_3AsO_3$: Oxidation state of As = +3.

   • In $H_3AsO_4$: Oxidation state of As = +5.

   • Arsenic goes from +3 to +5, meaning it loses electrons (oxidation).

2. For Bromine:

   • In $BrO_3$: Oxidation state of Br = +5.

   • In the product $Br$, bromine is in the elemental form with oxidation state 0.

   • Bromine goes from +5 to 0, meaning it gains electrons (reduction).

3. Conclusion:

   • Element undergoing reduction: Bromine (Br)
   • Element undergoing oxidation: Arsenic (As)

In $H_3AsO_3$, As is +3, which increases to +5 in $H_3AsO_4$ (oxidation). Bromine goes from +5 in $BrO_3$ to 0 in elemental $Br$ (reduction).