Redox Quiz #2

1. Which of the following pairs of ions will react spontaneously in a solution?

A. Cu²⁺ and Fe²⁺

B. Pb²⁺ and Sn²⁺

C. Co²⁺ and Cr²⁺

D. Mn²⁺ and Cr²⁺

2. When NO₂ reacts to form N₂O₄ the oxidation number of nitrogen

A. increases by 2

B. increases by 4

C. increases by 8

D. does not change

3. Consider the following redox equation:

12H⁺_(aq) + 2IO₃^-_(aq) + 10Fe²⁺_(aq) → 10Fe³⁺_(aq) + I_2(s) + 6H₂O_(l)

The reducing agent is

A. I₂

B. H⁺

C. Fe²⁺

D. IO₃^-

4. The oxidation number of nitrogen increases in

A. NO₃^- → NO

B. N₂O₄ → NI₃

C. NH₃ → NH₄⁺

D. NO₂ → N₂O₅

5. Which of the following represents a balanced reduction half-reaction?

A. VO₂ + 2H⁺ + 2e^- → V²⁺ + H₂O

B. VO₂ + H₂ → V²⁺ + H₂O + le^-

C. VO₂ + 2H⁺ + le^- → V²⁺ + H₂O

D. VO₂ + 4H⁺ + 2e^- → V²⁺ + 2H₂O

6. Consider the following half reaction:

Sb₂O₃ + 6H⁺ + 6e^- ⇄ 2Sb + 3H₂O

The oxidation number of antimony in Sb₂O₃

A. increases by 3

B. increases by 6

C. decreases by 3

D. decreases by 6

7. Consider the following unbalanced half-reaction

HClO₂ ⇄ HClO

The balanced half-reaction would have

A. 1 electron on the left

B. 1 electron on the right

C. 2 electrons on the left

D. 2 electrons on the right

8. The oxidation number of platinum in Pt(H₂O)₄²⁺ is

A. +2

B. 0

C. +4

D. +1/2

9. Consider the following half-reaction :

BrO^- → Br^- (basic)

The balanced equation for the half-reaction is

A. BrO^- + 2H⁺ + 2e^- → Br^- + H₂O

B. BrO^- + 2H⁺ → Br^- + H₂O + 2e^-

C. BrO^- + H₂O → Br^- + 2OH^- + 2e^-

D. BrO^- + H₂O + 2e^- → Br^- + 2OH^-

10. Consider the following redox reaction:

2MnO₄^- + 5CH₃CHO + 6H⁺ → 5CH₃COOH + 2Mn²⁺ + 3H₂O

The species that loses the electron is

A. H₂O

B. MnO₄^-

C. CH₃CHO

D. CH₃COOH

11. Hydrogen has an oxidation number of –1 in

A. H₂

B. NaH

C. H₂O

D. KOH

12. Consider the following:

2NO₃^- + 4H⁺ + 2e^- → N₂O₄ + 2H₂O

This equation represents

A. reduction

B. oxidation

C. neutralization

D. decomposition

13. Which of the following half-reactions is balanced?

A. IO₃^- + 6H⁺ +5e^- → I₂ + 3H₂O

B. IO₃^- + 6H⁺ + 4e^- →1/2 I₂ + 3H₂O

C. IO₃^- + 6H⁺ → ½ I₂ + 3H₂O + 5e^-

D. IO₃^- + 6H⁺ + 5e^- → ½ I₂ + 3H₂O

14. Consider the following redox reaction:

Al + MnO₄^- + 2H₂O →Al(OH)₄^- + MnO₂

The chemical species being oxidized is

A. Al

B. MnO₄^-

C. Al(OH)₄^-

D. MnO₂

15. Consider the following redox reaction:

6H⁺ + 6I^- + ClO₃^- → 3I₂ + 3H₂O + Cl^-

The reducing agent is

A. I^-

B. I₂

C. H⁺

D. ClO₃^-

16. Nitrogen has an oxidization number of zero in

A. N₂

B. NO₂

C. NH₃

D. HNO₃

17. When MnO₄^- reacts to form Mn²⁺, the manganese in MnO₄^- is

A. reduced as its oxidation number increases

B. reduced as its oxidation number decreases

C. oxidized as its oxidation number increases

D. oxidized as its oxidation number decreases

18. Consider the following reaction:

2HNO₃ + 3H₂S → 2NO + 3S + 4H₂O

The nitrogen in HNO₃ undergoes

A. reduction

B. oxidation

C. electrolysis

D. neutralization

19. The oxidation number in carbon in CaC₂O₄ is

A. +2

B. +3

C. +4

D. +6

20. Consider the following redox reaction:

2Cr3+(aq) + 3Cl2(aq) + 7H2O(l) → Cr2O72-(aq) + 6Cl-(aq) + 14H+(aq)

The species which loses electrons is

A. Cl₂

B. Cr³⁺

C. H₂O

D. Cr₂O₇^2-

21. Which equation represents a redox reaction?

A. Pb²⁺ + 2Cl^- → PbCl₂

B. CaO + CO₂ → CaCO₃

C. Mg + 2HCl → MgCl₂ + H₂

D. HCl + NaOH → NaCl + H₂O

22. In a redox reaction, ClO^- was converted to Cl^- in a basic solution. The balanced

half-reaction for this process is

A. ClO^- + H₂O + 2e^- → Cl^- + 2OH^-

B. ClO^- + 2OH^- → Cl^- + 2e^- + H₂O

C. ClO^- + H₂O → Cl^- + 2e^- + 2OH^-

D. ClO^- + 2OH^- + 2e^- → Cl^- + H₂O

23. Which of the following equations is not predicted to represent a redox reaction?
A. 2 H2O(l) + O2(g) ® 2 H2O2(l)
B. 2 Sn2+(aq) ® Sn(s) + Sn4+(aq)
C. Ag+(aq) + Cl-(aq) ® AgCl(s)
D. C2H4(g) + 3 O2(g) ® 2 CO2(g) + 2 H2O(g)

24. The metal molybdenum, Mo, can react to produce MoO_2(s). The half reaction that explains the change in oxidation state of

molybdenum can be written
A. Mo_(s) + 2e^- → Mo²⁺
B. Mo_(s) → Mo²⁺ + 2e^-
C. Mo⁴⁺ + 4e^- → Mo_(s)
D. Mo_(s) → Mo⁴⁺ + 4e^-

25. Which incomplete half-reaction is an oxidation?
A. 2H⁺ + 12 O_2(g) → H₂O_(l)
B. Cr₂O₇^2- + 14H⁺ → 2 Cr³⁺ + 7 H₂O_(l)
C. K⁺ → K_(s)
D. 2 I^- → I_2(s)

26. Which of these would react spontaneously with Co(s) but not with H2(g)?
A. H2O(l)
B. Ni2+(aq)
C. Ca2+(aq)
D. Br-(aq)

27. The chemical that will reduce copper (II) ions and also oxidize metallic nickel is

aqueous
A. iron (III) nitrate
B. tin (II) sulfate
C. iron (II) nitrate
D. zinc sulfate

28. F_2(g) is a strong reducing agent F_2(g) has a strong attraction for electrons. Based on this information, one should determine that

            A. the statement and the explanation are true, and that the explanation is

correct for the statement.
B. both the statement and the explanation are true, but the explanation is not

            correct for the statement.
C. the statement is true, but the explanation is false.
D. the statement is false, but the explanation is true

29. Solutions containing Fe2+(aq), Sn2+(aq) and Cr2+(aq) are mixed together. The reaction

most likely to occur is
A. 2Fe2+(aq) + 2 H2O(l) ® Fe(s) + O2(g) + 4H+(aq)
B. Sn2+(aq) + 2Cr2+(aq) ® Sn(s) + 2 Cr3+(aq)
C. Sn2+(aq) + Cr2+(aq) ® Sn4+(aq) + Cr(s)
D. Sn2+(aq) + 2 Fe2+(aq) ® Sn(s) + 2 Fe3+(aq)

30. Four reducing agents listed in order of decreasing strength are W, Z, Y and X. Four statements about the reaction

between the reducing agents and their respective oxidizing agents are:
I. W(s) + X2+(aq) ® W2+(aq) + X(s)
II. Y(s) + X2+(aq) ® Y2+(aq) + X(s)
III. W(s) + Z2+(aq) ® no reaction
IV. Y(s) + Z2+(aq) ® Y2+(aq) + Z(s)
The statement(s) inconsistent with the correct order of reducing agents is (are)
A. IV only
B. III only
C. I and II
D. III and IV