Chemistry MCQ with Answer and Explanation : Oxidation and Reduction.

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Question 81:

Which of the following represents a loss of electrons?
A) Reduction
B) Oxidation
C) Neutralization
D) Hydrolysis

Answer: B) Oxidation

Explanation: Oxidation is defined as the loss of electrons.

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Question 82:

What is the oxidation state of carbon in carbon dioxide (CO2CO2​)?
A) +4
B) +2
C) 0
D) -2

Answer: A) +4

Explanation: In carbon dioxide, carbon has an oxidation state of +4.

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Question 83:

Which of the following species is most likely to be reduced?
A) Na+Na+
B) Cl−Cl−
C) Cu2+Cu2+
D) Ca2+Ca2+

Answer: C) Cu2+Cu2+

Explanation: Copper ions can gain electrons to become elemental copper, making them likely to be reduced.

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Question 84:

Which of the following processes involves oxidation?
A) Fe2+→Fe3++e−Fe2+→Fe3++e−
B) Cu2++2e−→CuCu2++2e−→Cu
C) Ag+e−→Ag+Ag+e−→Ag+
D) O2+4e−→2O2−O2​+4e−→2O2−

Answer: A) Fe2+→Fe3++e−Fe2+→Fe3++e−

Explanation: This reaction shows iron losing an electron, which is oxidation.

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Question 85:

In the reaction 2MnO4−+5C2O42−+6H+→2Mn2++10CO2+3H2O2MnO4−​+5C2​O42−​+6H+→2Mn2++10CO2​+3H2​O, what happens to manganese?
A) It is oxidized.
B) It is reduced.
C) It remains unchanged.
D) None of the above.

Answer: B) It is reduced.

Explanation: Manganese is reduced from +7 in MnO4−MnO4−​ to +2 in Mn2+Mn2+.

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Question 86:

Which of the following substances can act as both an oxidizing and a reducing agent?
A) H2OH2​O
B) H2O2H2​O2​
C) NaClNaCl
D) NH3NH3​

Answer: B) H2O2H2​O2​

Explanation: Hydrogen peroxide can both gain and lose electrons, making it versatile in redox reactions.

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Question 87:

What is the oxidation state of iron in Fe2O3Fe2​O3​?
A) +2
B) +3
C) 0
D) -3

Answer: B) +3

Explanation: In iron(III) oxide (Fe2O3Fe2​O3​), iron has an oxidation state of +3.

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Question 88:

Which of the following is a common application of redox reactions?
A) Battery operation
B) Combustion processes
C) Corrosion
D) All of the above

Answer: D) All of the above

Explanation: Redox reactions play critical roles in batteries, combustion, and corrosion processes.

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Question 89:

What is the oxidation state of chlorine in ClO2−ClO2−​?
A) +1
B) +3
C) +4
D) -1

Answer: B) +3

Explanation: In the chlorite ion (ClO2−ClO2−​), chlorine has an oxidation state of +3.

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Question 90:

In the reaction 4Fe+3O2→2Fe2O34Fe+3O2​→2Fe2​O3​, what is happening to iron?
A) It is oxidized.
B) It is reduced.
C) It remains unchanged.
D) It is neutralized.

Answer: A) It is oxidized.

Explanation: Iron loses electrons to form Fe2O3Fe2​O3​, indicating oxidation.