Question

What is number of moles of electrons gained by one mole of oxidizing agent in the following reaction?

$Mn^{2+}_{(aq)} + 2ClO^{-}_{(aq)} \longrightarrow MnO_{2(s)} + 2ClO_{2(aq)}$

• A. 4
• B. 3
• C. 2
• D. 1

Answer 1

Zero

Answer 2

Solution:

1. In any redox reaction the oxidizing agent undergoes reduction (i.e. it gains electrons).

2. Check the oxidation‐states:

   • For Mn: In Mn²⁺ the oxidation state is +2; in MnO₂ (with O = –2) Mn is +4. This is an increase → oxidation.

   • For chlorine in ClO⁻: Let its oxidation number be x. Then:

     x + (–2) = –1 ⟹ x = +1.

     In ClO₂ the chlorine oxidation state (assuming oxygen remains –2) is:

     x + 2(–2) = 0 ⟹ x = +4.

     This is also an increase in oxidation state → oxidation.

3. Since both Mn²⁺ and ClO⁻ are oxidized, no species is being reduced; hence there is no oxidizing agent gaining electrons.

4. Answer: The number of moles of electrons gained by one mole of the oxidizing agent is 0.

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Summary of Response:

• Core Explanation:

  Both Mn²⁺ and ClO⁻ undergo an increase in oxidation state (from +2 to +4 for Mn, and from +1 to +4 for Cl) so neither is reduced. Therefore, the oxidizing agent (the species that should gain electrons) is absent – no electrons are gained.

• Answer: 0 (Zero electrons)

  (Since none of the given options (A) 4, (B) 3, (C) 2, (D) 1 matches, the correct answer is 0.)