Practice Problems for Balancing Redox Equations in Acid/Base

Redox Reactions in Acidic Solution:

1. I¯ (aq) + ClO¯(aq) ¾® I₃¯(aq) + Cl¯(aq)

2. As₂O₃ (s) + NO₃¯ (aq) ¾® H₃AsO₄ (aq) + NO (g)

3. Br¯ (aq) + MnO₄¯ (aq) ¾® Br₂ (l) + Mn²⁺ (aq)

4. CH₃OH (aq) + Cr₂O₇^2- (aq) ¾® CH₂O(l) + Cr³⁺(aq)

5. Mn²⁺(aq) + BiO₃¯ (aq) ¾® Bi³⁺(aq) + MnO₄¯ (aq)

6. S₈(s) + NO₃¯ (aq) ¾® SO₃^2-(aq) + NO(g)

7. H₃AsO₄(aq) + Zn(s) ¾® AsH₃(g) + Zn²⁺(aq)

8. P₄(s) + Cr₂O₇^2-(aq) ¾® H₃PO₄(aq) + Cr³⁺(aq)

Redox Reactions in Basic Solution

1. Al(s) + MnO₄¯ (aq) ¾® MnO₂(s) + Al(OH)₄¯ (aq)

2. NO₂¯ (aq) + Al(s) ¾® NH₃(aq) + AlO₂¯ (aq)

3. Cr(s) + CrO₄^2-(aq) ¾® Cr(OH)₃(s)

Note: Cr(OH)₃ is found in BOTH half reactions!

4. MnO₄¯ (aq) + S^2-(aq) ¾® MnO₂(s) + SO₃^2-(aq)

5. Cl₂(aq) + Br₂(l) ¾® OBr¯ (aq) + Cl¯ (aq)

6. H₂O₂(aq) + I¯ (aq) ¾® IO₃¯ (aq)

Note: IO₃¯ is found in both half reactons!

7. NO₃¯ (aq) + NH₃(aq) ¾® NO₂¯ (aq)

8. S₈(aq) + MnO₄¯ (aq) ¾® SO₄^2-(aq) + MnO₂(s)

ANSWER KEY NOT NEEDED! IF THE EQUATION MASS AND CHARGE BALANCES, IT CAN’T BE WRONG!