Oxidation and reduction

For each question choose the answer you consider to be the best.

1. Which is correct statement about reduction?

A. It involves the loss of hydrogen.

B. It involves the addition of oxygen.

C. It involves the addition of electrons.

D. It involves an increase in oxidation number.

2. In which species does manganese have an oxidation state of +3?

A. MnSO₄

B. KMnO₄

C. Mn₂O₃

D. MnO₂

3. What is the correct name for FeSO₄?

A. iron(II) sulfite

B. iron(III) sulfite

C. iron(II) sulfate

D. iron(II) sulfide

4. What change occurs to vanadium during the conversion of VO₃^–(aq) to VO²⁺?

A. It undergoes reduction and its oxidation state changes from + 5 to +4.

B. It undergoes reduction and its oxidation state changes from +3 to +2

C. It undergoes oxidation and its oxidation state changes from –1 to +2

D. It undergoes oxidation and its oxidation state changes from +6 to +2

5. What are the oxidation states of the elements in sulfuric acid, H₂SO₄?

6. Which are correct statements?

I. The oxidation state of oxygen in H₂O₂ is –1

II. The oxidation state of nitrogen in N₂H₄ is –2

III. The oxidation state of hydrogen in MgH₂ is –1

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

7. Which change involves nitrogen being oxidized?

A. N₂H₄ → NH₂^–

B. NO₂ → N₂O₄

C. NO₃^– → N₂O₅

D. N₂O → NO

8. Which is correct about the following reaction?

2I^–(aq) + Cl₂(aq) → I₂(aq) + 2Cl^–(aq)

A. I^–(aq) gains electrons and is reduced.

B. Cl₂(aq) loses electrons and is reduced.

C. I^–(aq) loses electrons and is oxidized.

D. Cl₂(aq) gains electrons and is oxidized.

9. Which changes are examples of reduction?

I. Cu²⁺ → Cu⁺

II. NH₃ → N₂

III. MnO₄^– MnO₂

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

10. Which is the correct order of the decreasing oxidising ability of the group 17 elements (strongest oxidizing agent first)?

A. F₂ > Cl₂ > Br₂ > I₂

B. Cl₂ > Br₂ > I₂ > F₂

C. I₂ > Br₂ > Cl₂ > F₂

D. F₂ > I₂ > Br₂ > Cl₂

11. Which reaction is not a redox reaction?

A. H₂S(g) + Cl₂(aq) → 2HCl(aq) + S(s)

B. Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g)

C. Ag⁺(aq) + Cl^–(aq) → AgCl(s)

D. 3H₂(g) + N₂(g) → 2NH₃(g)

12. In which reactions are carbon atoms oxidized?

I. C₂H₅OH → CH₃CHO + 2H⁺ + 2e^–

II. C₂H₄ + Br₂ → C₂H₄Br₂

III. C₂H₅Br + OH^– → C₂H₅OH + Br^–

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

13. What is the coefficient for H⁺(aq) when the redox equation below is balanced ?

MnO₄^–(aq) + Fe²⁺(aq) + H⁺(aq) → Mn²⁺(aq) + Fe³⁺(aq) +  H₂O(l)

A. 2

B. 4

C. 5

D. 8

14. Which is the correct combination of statements for the following reaction?

Cr₂O₇^2–- (aq) + 3H₂O₂(l) + 8H⁺(aq) → 2Cr³⁺(aq) + 3O₂ + 7H­₂O(l)

15. A voltaic cell is constructed from a half-cell consisting of a piece of iron in a solution of iron(II) ions connected to a half-cell consisting of a piece of copper in a solution of copper(II) ions. Iron is more reactive than copper. Which statement is correct?

A. Iron atoms lose electrons.

B. Electrons flow from the copper half-cell to the iron half-cell.

C. The mass of the negative electrode increases.

D. The concentration of Cu²⁺(aq) ions increases.

16. Consider the following reactions which all occur in solution at room temperature.

Fe(s) + Cu²⁺(aq) → Fe²⁺ + Cu(s)

Mg(s) + Zn²⁺(aq) → Mg²⁺ + Zn(s)

Zn(s) + Fe²⁺(aq) → Zn²⁺ + Fe(s)

Which is the correct combination of the strongest oxidizing agent and the strongest reducing agent?

17. What process occurs at the positive electrode in a voltaic cell and in an electrolytic cell?

18. Which occur during the electrolysis of molten sodium chloride?

I. Chlorine gas forms at the positive electrode

II. Electrons flow through the molten liquid

III. Reduction occurs at the negative electrode

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

19. Which are correct statements about cells?

I. Electrolytic cells contain a salt bridge

II. In a voltaic cell electrons are produced at the negative electrode

III. In an electrolytic cell cations accept electrons at the negative electrode

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

20. Which statement is correct about how current is conducted in an electrolytic cell?

A. Electrons move through the electrolyte and the external circuit.

B. Ions move through the electrolyte and through the external circuit.

C. Ions move through the salt bridge and electrons move through the external circuit.

D. Ions move through the electrolyte and electrons move through the external circuit.

Answers

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