2025 Redox Review

The oxidation number for sulfur in H₂SO₃ is:

• a. -6

• b. -4

• c. +4

• d. +6

• e. 0

• c. +4

The oxidation number for N in NH₄⁺¹ is:

• a. +5

• b. +1

• c. –3

• d. +3

• e. –1

• c. –3

What is “N” in the following reaction: HNO₃ + I₂ → HIO₃ + NO₂ + H₂O

• a. The reducing agent

• b. Not being changed.

• c. Atom being oxidized

• d. Atom being reduced

• d. Atom being reduced

What is “HNO₃” in the following reaction: HNO₃ + I₂ → HIO₃ + NO₂ + H₂O

• a. Not being changed

• b. The oxidizing agent

• c. The reducing agent

• d. A base

• b. The oxidizing agent

When balancing a redox reaction in an acid, what is added to balance hydrogen?

• a. H⁺

• b. H₂O

• c. OH^-1

• a. H⁺

When the equation Cr₂O₇ ^2- + Cl^- --> Cr³⁺ + Cl₂ (acidic solution) is balanced using the smallest whole-number coefficients, the coefficient of H⁺ is:

• a. 14

• b. 1

• c. 12

• d. 4

• e. 6

• a. 14

In the reaction shown below, what species is oxidized?
2NaI + Br₂ --> 2NaBr + I₂

• a. Br^-

• b. I^-

• c. I₂

• d. Br₂

• b. I^-

In the following reaction, which species is reduced?

8 NaI + 5H₂SO₄ -->4 I₂ + H₂S + 4Na₂SO₄ + 4H₂0

• a. hydrogen

• b. sulfur

• c. oxygen

• d. sodium

• b. sulfur

Which of the following statements is (are) true? Oxidation and reduction

• a. cannot occur independently of each other.

• b. accompany all chemical changes.

• c. describe the loss and gain of electron(s), respectively.

• d. result in a change in the oxidation states of the species involved.

• e. a, c, and d are true

• e. a, c, and d are true

In which of the following does nitrogen have an oxidation state of +4?

• a. NO₂

• b. NaNO₂

• c. N₂O

• d. HNO₃

• a. NO₂

What is the oxidation number for the Sulfur (S) in each of the following compounds?

1. H2S2O4

2. H2S

3. S8

4. H2S2O5

What is the oxidation number for the Sulfur (S) in each of the following compounds?

1. H2S2O4	2
2. H2S	-2
3. S8	0
4. H2S2O5	4