Redox and Electrochemistry
Name: ____________________________________
Thursday, May 08, 2008
1.
A diagram of a chemical cell and an equation are shown below.
When the switch is closed, electrons will flow from
1. the Pb(s) to the Cu(s)
3. the Pb2+(aq) to the Pb(s)
2. the Cu(s) to the Pb(s)
4. the Cu 2+(aq) to the Cu(s)
2.
Which statement is true about oxidation and reduction in an electrochemical cell?
1. Both occur at the anode.
3. Oxidation occurs at the anode and reduction occurs at the cathode.
2. Both occur at the cathode.
4. Oxidation occurs at the cathode and reduction occurs at the anode.
3.
Which process requires an external power source?
1. neutralization
2. synthesis
3. fermentation
4. electrolysis
Redox and Electrochemistry
4.
An electrolytic cell is different from a voltaic cell because in an electrolytic cell
1. a redox reaction occurs
2. a spontaneous reaction occurs
3. an electric current is produced
4. an electric current causes a chemical reaction
5.
What is the oxidation number of nitrogen in NO(g)?
Answer:
6.
Which half-reaction correctly represents a reduction reaction?
1. Sn0 + 2eSn2+
0
2. Na + e
Na+
3. Li0 + eLi+
0
4. Br2 + 2e
2Br-
7.
What is the oxidation number of chlorine in HClO4?
1. +1
2. +5
3. +3
4. +7
8.
Which type of reaction is occurring when a metal undergoes corrosion?
1. oxidation-reduction
2. neutralization
3. polymerization
4. saponification
Redox and Electrochemistry
9.
Which statement best describes the reaction represented by the equation below?
2NaCl + 2H 2O + electricity
Cl2 + H 2 + 2NaOH
1. The reaction occurs in a voltaic cell and releases
energy.
2. The reaction occurs in a voltaic cell and absorbs
energy.
3. The reaction occurs in an electrolytic cell and releases
energy.
4. The reaction occurs in an electrolytic cell and absorbs
energy.
10.
Which changes occur when Pt2+ is reduced?
1. The Pt2+ gains electrons and its oxidation number
increases.
3. The Pt2+ loses electrons and its oxidation number
increases.
2. The Pt2+ gains electrons and its oxidation number
decreases.
4. The Pt2+ loses electrons and its oxidation number
decreases.
11.
Which quantities are conserved in all oxidation-reduction reactions?
1. charge, only
2. mass, only
3. both charge and mass
4. neither charge nor mass
12.
In the reaction: Pb + 2Ag+ → Pb2+ + 2Ag, the Ag+ is
1. reduced, and the oxidation number changes from +1
to 0
2. reduced, and the oxidation number changes from +2
to 0
3. oxidized, and the oxidation number changes from 0 to
+1
4. oxidized, and the oxidation number changes from +1
to 0
Redox and Electrochemistry
13.
In the redox reaction: Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s), there is a conservation of
1. mass, only
2. charge, only
3. both mass and charge
4. neither mass nor charge
14.
Which statement correctly describes a redox reaction?
1. The oxidation half-reaction and the reduction
half-reaction occur simultaneously.
2. The oxidation half-reaction occurs before the
reduction half-reaction.
15.
Given the reaction: Fe(s) + Sn4+(aq)
The oxidizing agent is
1. Fe(s)
3. Fe2+(aq)
2. Sn4+(aq)
4. Sn2+(aq)
3. The oxidation half-reaction occurs after the reduction
half-reaction.
4. The oxidation half-reaction occurs spontaneously but
the reduction half-reaction does not.
Fe2+(aq) + Sn2+(aq)
16.
What is the oxidation number of carbon in NaHCO3?
1. +6
2. +2
3. -4
4. +4
17.
Which equation shows conservation of both mass and charge?
1. Cl2 + Br- → Cl- + Br2
3. Zn + Cr3+ → Zn2+ + Cr
2. Cu + 2 Ag+ → Cu2+ + Ag
4. Ni + Pb2+ → Ni2+ + Pb
Redox and Electrochemistry
18.
An electrochemical cell that generates electricity contains half-cells that produce
1. oxidation half-reactions, only
2. reduction half-reactions, only
3. spontaneous redox reactions
4. nonspontaneous redox reactions
19.
Which half-reaction correctly represents reduction?
1. Fe2+ + 2eFe0
2+
2. Fe + e
Fe3+
0
3. Fe + 2e
Fe2+
4. Fe0 + eFe3+
20.
A discharging lead-acid battery is best described as
1. chemical cells that use an electric current
2. chemical cells that produce an electric current
3. electrolytic cells that use an electric current
4. electrolytic cells that produce an electric current
21.
A voltaic cell differs from an electrolytic cell in that a chemical cell uses
1. half-reactions
2. a solution of ions
3. an applied electric current
4. a redox reaction to produce electricity
22.
Which is a redox reaction?
1. H+ + Cl- → HCl
3. Fe + 2HCl → FeCl2 + H2
2. NaOH + HCl → NaCl + H 2O
4. MgO + H 2SO4 → MgSO4 + H 2O
Redox and Electrochemistry
23.
Which change occurs when an Sn 2+ ion is oxidized?
1. Two electrons are lost.
2. Two electrons are gained.
3. Two protons are lost.
4. Two protons are gained.
24.
Given the balanced ionic equation representing a reaction:
2Al3+(aq) + 3Mg(s)
3Mg2+(aq) + 2Al(s)
In this reaction, electrons are transferred from
1. Al to Mg2+
3. Mg to Al3+
2. Al3+ to Mg
4. Mg2+ to Al
25.
Which type of reaction occurs when nonmetal atoms become negative nonmetal ions?
1. oxidation
2. reduction
3. substitution
4. condensation
Redox and Electrochemistry
26.
Figure 1
Which type of cell does the diagram represent?
1. electrolytic, with the anode at A
2. electrolytic, with the cathode at A
3. voltaic , with the anode at A
4. voltaic , with the cathode at A
27.
A student collects the materials and equipment below to construct a voltaic cell.
two 250-mL beakers
wire and a switch
one strip of magnesium
one strip of copper
125 mL of 0.20 M Mg(NO3)2(aq)
125 mL of 0.20 M Cu(NO3)2(aq)
Which additional item is required for the construction of the voltaic cell?
1. an anode
3. a cathode
2. a battery
4. a salt bridge
Redox and Electrochemistry
28.
Figure 2
The diagram slows the electrolysis of fused KCl. What occurs when the switch is closed?
1. Positive ions migrate toward the anode, where they
lose electrons.
2. Positive ions migrate toward the anode, where they
gain electrons.
3. Positive ions migrate toward the cathode, where they
lose electrons.
4. Positive ions migrate toward the cathode, where they
gain electrons.
29.
Which particles are gained and lost during a redox reaction?
1. electrons
2. protons
3. neutrons
4. positrons
30.
Given the reaction: 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g )
Which substance undergoes oxidation?
1. Na
2. NaOH
3. H2
4. H2O
Redox and Electrochemistry
31.
Which balanced equation represents an oxidation-reduction reaction?
1. BaCl2 + Na2SO4
BaSO4 + 2NaCl
2. C + H 2O
CO + H2
3. CaCO3
CaO + CO2
4. Mg(OH)2 + 2HNO3
Mg(NO3)2 + 2H2O
32.
When the equation
__Pb2+ + __Au 3+ → __Pb4+ + __Au
is correctly balanced using the smallest whole-number coefficients, the coefficient of Pb2+ will be
1. 1
2. 2
3. 3
4. 4
33.
Which half-cell reaction correctly represents reduction?
1. Cu+(aq) + eCu(s)
2+
2. Cu(s)
Cu (aq) + 2e3. H(g) + e
H+(aq)
4. H2(g)
2H+(aq) + 2e-
Redox and Electrochemistry
34.
Figure 3
Write the balanced half-reaction for the reduction that occurs in this electrolytic cell.
1. Cl2 + 2e2Cl2. Cl2
2Cl- + 2e3. 2Na+ + 2e2Na
4. 2Na+
2Na + 2e-
35.
Given the reaction: 2Li(s) + Cl2(g)
2LiCl(s)
As the reaction takes place, the Cl 2(g) will
1. gain electrons
2. lose electrons
3. gain protons
4. lose protons
36.
The purpose of a salt bridge in a voltaic cell is to
1. allow for the flow of molecules between the solutions
2. allow for the flow of ions between the solutions
3. prevent the flow of molecules between the solutions
4. prevent the flow of ions between the solutions
Redox and Electrochemistry
37.
Which statement is true for any electrochemical cell?
1. Oxidation occurs at the anode, only.
2. Reduction occurs at the anode, only.
3. Oxidation occurs at both the anode and the cathode.
4. Reduction occurs at both the anode and the cathode.
38.
In which compound does sulfur have an oxidation number of -2?
1. SO2
2. SO3
3. Na2S
4. Na2SO4
39.
Figure 4
The diagram represents a chemical cell at 298 K and 1 atmosphere. Which species represents the cathode?
1. Zn
2. Zn2+
3. Cu
4. Cu2+
Redox and Electrochemistry
40.
Given the reaction:
Which species undergoes reduction?
1. Al
3. Al3+
2. Fe
4. Fe3+
41.
What is the purpose of the salt bridge in a voltaic cell?
1. It blocks the flow of electrons.
2. It blocks the flow of positive and negative ions.
3. It is a path for the flow of electrons.
4. It is a path for the flow of positive and negative ions.
42.
Given the balanced equation: 3Fe 3+(aq) + Al(s) → 3Fe2+(aq) + Al3+(aq)
What is the total number of moles of electrons lost by 2 moles of Al(s)?
1. 1 mole
2. 6 moles
3. 3 moles
4. 9 moles
43.
Given the reaction: Ca(s) + Cu2+(aq) → Ca2+(aq) + Cu(s)
What is the correct reduction half-reaction?
1. Cu2+(aq) + 2e- → Cu(s)
3. Cu(s) + 2e- → Cu2+(aq)
2. Cu2+(aq) → Cu(s) + 2e-
4. Cu(s) → Cu2+(aq) + 2e-
44.
Given the redox reaction: Ni + Sn4+
Which species has been oxidized?
1. Ni
3. Ni2+
2. Sn4+
4. Sn2+
Ni2+ + Sn2+
Redox and Electrochemistry
45.
Figure 5
The diagram shows an electrolytic cell in which the electrodes are tin and copper. When the switch is closed, what will
happen to the two electrodes?
1. B will dissolve and A will become coated with tin.
2. A will dissolve and B will become coated with tin.
3. B will dissolve and A will become coated with copper.
4. A will dissolve and B will become coated with copper.
46.
Figure 6
The diagram represents the electroplating of a metal fork with Ag( s). Which part of the electroplating is represented
by the fork?
1. the anode, which is the negative electrode
2. the cathode, which is the negative electrode
3. the anode, which is the positive electrode
4. the cathode, which is the positive electrode
Redox and Electrochemistry
47.
Given the redox reaction: Fe2+(aq) + Zn(s)
Which species acts as a reducing agent?
1. Fe(s)
2. Fe2+(aq)
Zn2+(aq) + Fe(s)
3. Zn(s)
4. Zn2+(aq)
48.
Given the balanced ionic equation:
Zn(s) + Cu2+(aq) → Zn 2+(aq) + Cu(s)
Which equation represents the oxidation half-reaction?
1. Zn(s) + 2e- → Zn2+(aq)
3. Cu2+ (aq) →Cu(s) + 2e-
2. Zn(s) → Zn 2+(aq) + 2e-
4. Cu2+ (aq) + 2e- → Cu(s)
49.
Which energy conversion occurs during the operation of a voltaic cell?
1. Chemical energy is spontaneously converted to
3. Electrical energy is spontaneously converted to
electrical energy.
chemical energy.
2. Chemical energy is converted to electrical energy only
4. Electrical energy is converted to chemical energy only
when an external power source is provided.
when an external power source is provided.
50.
In which substance does chlorine have an oxidation number of +1?
1. Cl2
2. HCl
3. HClO
4. HClO2
Redox and Electrochemistry
Answer Key for Redox and Electrochemistry
1. 1
2. 3
3. 4
4. 4
5. +2
6. 4
7. 4
8. 1
9. 4
10. 2
11. 3
12. 1
13. 3
14. 1
15. 2
16. 4
17. 4
18. 3
19. 1
20. 2
21. 4
22. 3
23. 1
24. 3
25. 2
26. 1
27. 4
28. 4
29. 1
30. 1
31. 2
32. 3
33. 1
34. 3
35. 1
36. 2
37. 1
38. 3
39. 3
40. 4
41. 4
42. 2
43. 1
44. 1
45. 2
46. 2
Redox and Electrochemistry
47. 3
48. 2
49. 1
50. 3