Redox Reactions
Q. In a galvanic cell, which electrode undergoes reduction?
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A.
Anode
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B.
Cathode
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C.
Salt bridge
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D.
Electrolyte
Solution
In a galvanic cell, reduction occurs at the cathode.
Correct Answer: B — Cathode
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Q. In a redox reaction, which species is reduced?
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A.
Oxidizing agent
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B.
Reducing agent
-
C.
Product
-
D.
Reactant
Solution
The oxidizing agent is the species that gains electrons and is reduced.
Correct Answer: A — Oxidizing agent
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Q. In the reaction 2Ag+ + Zn → 2Ag + Zn2+, which species is oxidized?
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A.
Ag+
-
B.
Zn
-
C.
Ag
-
D.
Zn2+
Solution
Zinc (Zn) is oxidized to Zn2+.
Correct Answer: B — Zn
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Q. In the reaction 2Ag+ + Zn → 2Ag + Zn2+, which species is reduced?
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A.
Ag+
-
B.
Zn
-
C.
Ag
-
D.
Zn2+
Solution
Ag+ is reduced as it gains electrons to form Ag.
Correct Answer: A — Ag+
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Q. In the reaction 2AgNO3 + Cu → 2Ag + Cu(NO3)2, what is the oxidation state of silver in AgNO3?
Solution
In AgNO3, silver has an oxidation state of +1.
Correct Answer: A — +1
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Q. In the reaction 2Ag^+ + Zn → 2Ag + Zn^2+, what is the oxidation state change for zinc?
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A.
0 to +2
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B.
+2 to 0
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C.
+2 to +1
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D.
0 to -1
Solution
Zinc is oxidized from an oxidation state of 0 to +2.
Correct Answer: A — 0 to +2
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Q. In the reaction 2Cr2O7^2- + 14H+ + 6e^- → 4Cr^3+ + 7H2O, what is the role of Cr2O7^2-?
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A.
Oxidizing agent
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B.
Reducing agent
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C.
Neutral agent
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D.
None of the above
Solution
Cr2O7^2- is reduced to Cr^3+, making it the oxidizing agent.
Correct Answer: A — Oxidizing agent
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Q. In the reaction 2Fe2O3 + 3C → 4Fe + 3CO2, what is being oxidized?
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A.
Fe2O3
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B.
C
-
C.
Fe
-
D.
CO2
Solution
Carbon (C) is being oxidized to carbon dioxide (CO2).
Correct Answer: B — C
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Q. In the reaction 2Fe2O3 + 3C → 4Fe + 3CO2, what is being reduced?
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A.
Fe2O3
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B.
C
-
C.
Fe
-
D.
CO2
Solution
Fe2O3 is being reduced to Fe as it gains electrons.
Correct Answer: A — Fe2O3
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Q. In the reaction 2Fe2O3 + 3C → 4Fe + 3CO2, which element is oxidized?
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A.
Iron
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B.
Carbon
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C.
Oxygen
-
D.
None
Solution
Carbon is oxidized as it loses electrons to form CO2.
Correct Answer: B — Carbon
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Q. In the reaction 2Fe^3+ + 2I^- → 2Fe^2+ + I2, which species is the reducing agent?
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A.
Fe^3+
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B.
I^-
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C.
Fe^2+
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D.
I2
Solution
I^- donates electrons to Fe^3+, thus it is the reducing agent.
Correct Answer: B — I^-
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Q. In the reaction 2H2 + O2 → 2H2O, which element is oxidized?
Solution
Oxygen (O) is oxidized as it goes from 0 in O2 to -2 in H2O.
Correct Answer: B — O
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Q. In the reaction 3H2 + N2 → 2NH3, which element is oxidized?
Solution
Hydrogen (H) is oxidized as it goes from an oxidation state of 0 to +1 in NH3.
Correct Answer: A — H
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Q. In the reaction 4Fe + 3O2 → 2Fe2O3, what is the oxidation state of iron in Fe2O3?
Solution
In Fe2O3, iron has an oxidation state of +3.
Correct Answer: B — +3
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Q. In the redox reaction 2Fe2O3 + 3C → 4Fe + 3CO2, what is the oxidation state of carbon in CO2?
Solution
In CO2, the oxidation state of carbon is +4.
Correct Answer: C — +4
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Q. What is the change in oxidation state of carbon in the reaction: CH4 + 2O2 → CO2 + 2H2O?
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A.
0 to +4
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B.
+4 to 0
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C.
0 to -4
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D.
-4 to 0
Solution
The oxidation state of carbon changes from -4 in CH4 to +4 in CO2.
Correct Answer: A — 0 to +4
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Q. What is the oxidation state of chlorine in NaClO3?
Solution
In NaClO3, chlorine has an oxidation state of +5.
Correct Answer: C — +5
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Q. What is the oxidation state of nitrogen in NH4+?
Solution
In NH4+, nitrogen has an oxidation state of -3.
Correct Answer: A — -3
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Q. What is the oxidation state of nitrogen in NO3^-?
Solution
In NO3^-, nitrogen has an oxidation state of +5.
Correct Answer: B — +5
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Q. What is the oxidation state of sulfur in H2SO4?
Solution
In H2SO4, the oxidation state of sulfur is +6.
Correct Answer: C — +6
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Q. What is the product formed when Fe2O3 is reduced by carbon monoxide?
Solution
The product formed is Fe (iron) when Fe2O3 is reduced by carbon monoxide.
Correct Answer: A — Fe
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Q. What is the reducing agent in the reaction 2MnO4- + 5C2O4^2- + 6H+ → 2Mn^2+ + 10CO2 + 3H2O?
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A.
MnO4-
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B.
C2O4^2-
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C.
H+
-
D.
CO2
Solution
C2O4^2- is the reducing agent as it donates electrons.
Correct Answer: B — C2O4^2-
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Q. What is the reducing agent in the reaction Zn + CuSO4 → ZnSO4 + Cu?
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A.
Zn
-
B.
Cu
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C.
CuSO4
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D.
ZnSO4
Solution
Zinc (Zn) is the reducing agent as it donates electrons to copper.
Correct Answer: A — Zn
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Q. What is the reduction half-reaction for the conversion of MnO4- to Mn2+ in acidic medium?
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A.
MnO4- + 8H+ + 5e- → Mn2+ + 4H2O
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B.
MnO4- + 5e- → Mn2+ + 8H+ + 4H2O
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C.
MnO4- + 4H2O + 5e- → Mn2+ + 8H+
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D.
MnO4- + 5e- + 4H2O → Mn2+ + 8H+
Solution
The correct reduction half-reaction in acidic medium is MnO4- + 8H+ + 5e- → Mn2+ + 4H2O.
Correct Answer: A — MnO4- + 8H+ + 5e- → Mn2+ + 4H2O
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Q. What is the reduction half-reaction for the reaction 2MnO4- + 16H+ + 10e- → 2Mn2+ + 8H2O?
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A.
MnO4- + 8H2O + 10e- → Mn2+ + 16H+
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B.
MnO4- + 10e- + 8H+ → Mn2+ + 4H2O
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C.
MnO4- + 10e- → Mn2+ + 8H2O
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D.
MnO4- + 16H+ → Mn2+ + 10e- + 8H2O
Solution
The correct reduction half-reaction shows the gain of electrons and protons.
Correct Answer: B — MnO4- + 10e- + 8H+ → Mn2+ + 4H2O
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Q. What is the reduction half-reaction for the reaction of copper(II) ions with zinc?
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A.
Cu^2+ + 2e^- → Cu
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B.
Zn → Zn^2+ + 2e^-
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C.
Cu → Cu^2+ + 2e^-
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D.
Zn^2+ + 2e^- → Zn
Solution
The reduction half-reaction is Cu^2+ + 2e^- → Cu.
Correct Answer: A — Cu^2+ + 2e^- → Cu
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Q. What is the role of a catalyst in a redox reaction?
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A.
Increase oxidation
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B.
Increase reduction
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C.
Speed up the reaction
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D.
Change the products
Solution
A catalyst speeds up the reaction without being consumed in the process.
Correct Answer: C — Speed up the reaction
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Q. Which of the following compounds can act as a reducing agent?
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A.
H2O2
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B.
Cl2
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C.
Na
-
D.
O2
Solution
Sodium (Na) can act as a reducing agent as it readily donates electrons.
Correct Answer: C — Na
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Q. Which of the following compounds can act as an oxidizing agent?
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A.
NaCl
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B.
H2O
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C.
KMnO4
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D.
C6H12O6
Solution
KMnO4 is a strong oxidizing agent due to the presence of Mn in a high oxidation state.
Correct Answer: C — KMnO4
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Q. Which of the following elements can act as a reducing agent?
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A.
Cl2
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B.
H2O
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C.
Na
-
D.
O2
Solution
Sodium (Na) can act as a reducing agent as it can donate electrons.
Correct Answer: C — Na
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