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Home/ Chemistry/Chemistry MCQ with Answer and Explanation : Oxidation and Reduction.

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On: October 6, 2024 Posted in Chemistry, Education, Exam Comments: 0 Views: 231

Chemistry MCQ with Answer and Explanation : Oxidation and Reduction.

Question 21:

In which of the following reactions does the oxidation state of iron decrease?
A) Fe2O3+3CO→2Fe+3CO2Fe2​O3​+3CO→2Fe+3CO2​
B) 4Fe+3O2→2Fe2O34Fe+3O2​→2Fe2​O3​
C) Fe+Cl2→FeCl2Fe+Cl2​→FeCl2​
D) Fe3++3e−→FeFe3++3e−→Fe

Answer: D) Fe3++3e−→FeFe3++3e−→Fe

Explanation: In this reaction, iron’s oxidation state decreases from +3 to 0, indicating reduction.

Question 22:

In a redox reaction, which species undergoes oxidation?
A) The species that gains electrons.
B) The species that loses electrons.
C) The species that remains unchanged.
D) None of the above.

Answer: B) The species that loses electrons.

Explanation: Oxidation is characterized by the loss of electrons.

Question 23:

In the reaction 4Al+3O2→2Al2O34Al+3O2​→2Al2​O3​, which element is oxidized?
A) Al
B) O
C) Al2O3Al2​O3​
D) None of the above

Answer: A) Al

Explanation: Aluminum is oxidized from 0 in elemental form to +3 in Al2O3Al2​O3​.

Question 24:

Which of the following can act as both an oxidizing and reducing agent?
A) H2OH2​O
B) H2O2H2​O2​
C) Cl2Cl2​
D) SO2SO2​

Answer: B) H2O2H2​O2​

Explanation: Hydrogen peroxide (H2O2H2​O2​) can act as an oxidizing agent by accepting electrons or as a reducing agent by donating electrons.

Question 25:

What is the oxidation state of manganese in MnO4−MnO4−​?
A) +4
B) +6
C) +7
D) +2

Answer: C) +7

Explanation: In permanganate ion MnO4−MnO4−​, the oxidation state of manganese is +7, calculated as follows: x+4(−2)=−1x+4(−2)=−1 leads to x=+7x=+7.

Question 26:

Which of the following is a strong reducing agent?
A) H2OH2​O
B) NaNa
C) Cl2Cl2​
D) H2O2H2​O2​

Answer: B) NaNa

Explanation: Sodium is a strong reducing agent because it readily loses electrons to form Na+Na+.

Question 27:

In the reaction 2Mg+O2→2MgO2Mg+O2​→2MgO, which element is reduced?
A) Mg
B) O
C) Both Mg and O
D) None of the above

Answer: B) O

Explanation: Oxygen is reduced as it gains electrons to go from 0 in O2O2​ to -2 in MgOMgO.

Question 28:

What is the oxidation state of chromium in Cr2O72−Cr2​O72−​?
A) +3
B) +4
C) +6
D) +2

Answer: C) +6

Explanation: In dichromate ion Cr2O72−Cr2​O72−​, the oxidation state of chromium is +6, calculated as follows: 2x+7(−2)=−22x+7(−2)=−2 leads to x=+6x=+6.

Question 29:

In the reaction 2H2+O2→2H2O2H2​+O2​→2H2​O, what is the reducing agent?
A) H2H2​
B) O2O2​
C) H2OH2​O
D) None of the above

Answer: A) H2H2​

Explanation: Hydrogen gas H2H2​ donates electrons and is oxidized, thus acting as the reducing agent.

Question 30:

Which of the following changes represents a reduction?
A) Cu2++2e−→CuCu2++2e−→Cu
B) Ag→Ag++e−Ag→Ag++e−
C) Fe3+→Fe2++e−Fe3+→Fe2++e−
D) Cl−→Cl2+2e−Cl−→Cl2​+2e−

Answer: A) Cu2++2e−→CuCu2++2e−→Cu

Explanation: This reaction shows the gain of electrons by copper ions, indicating a reduction process.

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