textbook redox part 1

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Multiple-Choice Questions

Circle the letter for the choice that best completes the statement or answers the question.

1. During oxidation

a) an atom gains neutrons

b) an atom gains electrons

c) an atom loses electrons

d) an atom loses neutrons

2. In the reaction 2Ag_{(aq) + Fe(s)}__{2Ag(s) + Fe}2_{(aq), what is the half-reaction}

representing reduction?

a) Fe(s)  2Ag_{(aq) + 2e}

b) Ag(s) + 1e __Ag_(aq)

c) Fe(s) 2e__Fe2_(aq)

d) Ag_{(aq) + 1e} __Ag(s)

3. A reducing agent may be an atom that a) gains neutrons

b) gains electrons c) loses electrons d) loses neutrons

4. In the reaction 6Na(s) + Cr2O72_{(aq) + 14H}_(aq)__2Cr3_{(aq) + 6Na}_{(aq) +}

7H2O(l), what is the oxidizing agent?

a) H_(aq)

b) Cr2O72_(aq)

c) Na(s)

d) Cr3_(Aq)

5. Which one of the following represents a redox reaction?

a) 2Na(s) + Cl2(g)  2NaCl(aq)

b) 2AgCl(aq) + Fe(NO3)2(aq)  FeCl2(aq) + 2AgNO3(aq) c) LiF(aq) + KBr(aq)  KF(aq) + LiBr(aq)

d) SnSO4(aq) + Ca(NO3)2(aq)  CaSO4(aq) + Sn(NO3)2(aq)

6. Which one of the following is not a redox reaction?

a) 2NaCl(aq) + Br2(l)  2NaBr(aq) + Cl2(g) b) CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) c) AgCl(aq) + Li(s)  Ag(s) + LiCl(aq)

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7. Using the following information, list the metal ions in order of increasing reactivity.

B+_{(aq) + D(s)}__D+_{(aq) + B(s)}

D+_{(aq) + C(s)}__{o reaction}

C+_{(aq) + B(s)}__B+_{(aq) + C(s)}

a) C_{, B}_{, D}

b) D_{, C}_{, B}

c) D_{, B}_{, C}

d) B, D_{, C}

8. Which metal in question 7 is the strongest reducing agent?

a) B b) D

c) C

d) not enough information to answer

Use the following table to answer questions 9 and 10.

Oxidation-Reduction Table

Strongest Oxidizing Agent

Weakest Reducing Agent Au+_(aq) _Au(s) Pt2+_(aq) _Pt(s) Ag2+_(aq) _Ag(s) Hg2+_(aq) _Hg(s) Cu2+_(aq) _Cu(s) Sn2+_(aq) _Sn(s) Ni2+_(aq) _Ni(s) Co2+_(aq) _Co(s) Tl+_(aq) _Tl(s) Cd2+_(aq) _Cd(s)

Fe2+_(aq) _Fe(s) Cr3+_(aq) _Cr(s) Zn2+_(aq) _Zn(s) Al3+_(aq) _Al(s) Mg2+_(aq) _Mg(s)

Ca2+_(aq) _Ca(s) Ba2+_(aq) _Ba(s) Weakest

Oxidizing Agent

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9. Refer to the “Oxidation-Reduction” table to determine which metal can reduce Co2+ (aq). a) gold b) silver c) copper d) zinc

10. Refer to the “Oxidation-Reduction” table to determine which ion can oxidize

Co(s).

a) Ca2+_(aq) b) Zn2+_(aq) c) Fe2+_(aq) d) Cu2+_(aq)

11. A disproportionation reaction is one in which

a) no oxidation or reduction occurs

b) different atoms of the same element are oxidized and reduced

c) one compound is reduced but no compounds are oxidized

d) one compound reduces two other compounds

12. What is the oxidation number of sulfur in sulfuric acid?

a) +8

b) +6

c) +4

d) +2

13. What is the change in oxidation number for nitrogen in the following

reaction?

N2(g) + 3H2(g)  2NH3(g)

a) 0  +3 b) –3  0 c) 0  3 d) –3  +3

14. Which change would be classed as an oxidation?

a) Cr2__Cr3

b) 2H __H2

c) Br2  2Br

d) Mg2__Mg

15. When the half-reaction Cr2O72__Cr3_{is balanced in acid solution, how}

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c) 2

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Numerical Response Questions

For each numerical response question, record the answer in the following response box.

16.

17. 18.

19.

20.

16. What is the oxidation number for carbon in each of the following

compounds?

CO CO2 CH4 C2H6

17. What is the oxidation number for sulfur in each of the following

compounds?

SO2 SO3 SO H2SO3

18. In a reaction between copper metal and aqueous iron(III) chloride, Fe3_is

reduced to Fe2_{(aq), while Cu(s) is oxidized to Cu}2+_{(aq). Determine the mass}

of Cu(s) required to react with 50 mL of 1.3 mol/L FeCl3(aq).

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20. 46.5 g of chlorine gas is reacted with 96.2 g of silver to form silver chloride, AgCl(s). Determine the mass of oxidizing reagent that reacts.

Written Response Questions

Answer each question in the space provided. Use complete sentences, show problem-solving methods (with formulas), and include diagrams (with labels) when required.

21. An acidified solution of permanganate ion, MnO4_{(aq), reacts with aqueous}

chloride ion, Cl_(aq).

a) In the reaction, MnO4_{oxidizes the chloride ions, while the manganese}

is reduced to Mn2+_{. Write the equations for the two half-reactions that}

will take place.

_________________________________________________________________________________

b) Balance the equation for the overall reaction.

_________________________________________________________________________________

c) A 100.0 mL sample of NaCl(aq) is reacted with 21.0 mL of 1.30 mol/L

KMnO4(aq). What is the concentration of NaCl(aq)?

________________________________________________________________________________

_________________________________________________________________________________

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22. a) Balance the equation for the reaction between bromine, Br2(aq), and

aqueous iodate ion, IO3_{(aq), in basic solution: Br2(aq) + IO3}_(aq)

 Br_{+ IO4}_(aq)

_________________________________________________________________________________

b) What volume of 0.788 mol/L KIO3(aq) will react with 4.00 g Br2(aq)?

_________________________________________________________________________________

23. Balance the reaction I_{(aq) + S2O8}2_{(aq)  I3}_{+ SO2(g) in acid solution.}

_________________________________________________________________________________

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Answers to Multiple-Choice Questions 1. c

2. d 3. c 4. b 5. a 6. d 7. c 8. b 9. d 10. d 11. b 12. b 13. c 14. a 15. a

Answers to Numerical Response Questions

16. CO: +2; CO2: +4; CH4: 4; C2H6: 3

17. SO2: +4; SO3: +6; SO: +2; H2SO3: +4

18. 2.1 g

19. 6.1 g

20. 31.6 g Cl2

Answers to Written Response Questions

21. a) Oxidation : 2Cl_{(aq)  2e}_{ Cl2(g)}

Reduction: MnO4_{(aq) + 8H}_{+ 5e}_{ Mn}2_{(aq) + 4H2O(}_l₎

b) 5  oxidation half-reaction: 10Cl_{(aq)  10e}_{ 5Cl2(g)}

2  reduction half-reaction: 2MnO4_{(aq) + 16H}_{(aq) + 10e}_{ 2Mn}2_{(aq) + 8H2O(}_l₎

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c) n(MnO4 ) = c  V = 1.3 mol/L  0.021 L = 0.0273 mol = 0.1365 mol Cl

n( NaCl) = = 1.36 mol/L

22. a) Br2(aq) + IO3_{(aq)  Br}_{(aq) + IO4}_(aq)

Reduction: Br2(aq) + 2e_{ 2Br}_(aq)

Oxidation : IO3_{(aq)  IO4}_(aq)

IO3(aq) + H2O(l)  IO4_{(aq) + 2H}_(aq)

IO3(aq) + H2O(l) + 2OH(aq)  IO4_{(aq) + 2H}_{(aq) + 2OH}_(aq)

IO3(aq) + 2OH(aq)  IO4_{(aq) + H2O(}_l_{) + 2e}

Add the two balanced half-reactions:

Br2(aq) + IO3_{(aq) + 2OH}_{(aq) IO4}_{(aq) + 2Br}_{(aq) + H2O(}_l₎

b) n(Br2) = = 0.02503 mol

n(KIO3) = = 0.02503 mol KIO3(aq)

V(KIO3) = = 0.03176 L = 31.8 mL

23. I(aq) + S2O82_{(aq)  I3}_{+ SO2(g)}

Oxidation: 3I_{(aq)  I3}_{(aq) + 2e}

Reduction: S2O82_{(aq)  2SO2(g)}

S2O82_{(aq)  2SO2(g) + 4H2O(}_l₎

8H_{(aq) + S2O8}2_{(aq)  2SO2(g) + 4H2O(}_l₎

8H_{(aq) + S2O8}2_{(aq) + 6e}_{ 2SO2(g) + 4H2O(}_l₎

Oxidation  3: 9I_{(aq)  3I3}_{(aq) + 6e}