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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: 225

Chemistry MCQ with Answer and Explanation : Oxidation and Reduction.

Question 31:

What is the oxidation state of carbon in CH4CH4​?
A) -4
B) +4
C) 0
D) +2

Answer: A) -4

Explanation: In methane (CH4CH4​), the oxidation state of carbon is -4, as it is bonded to hydrogen atoms that have an oxidation state of +1.

Question 32:

Which of the following represents an oxidation reaction?
A) Fe3++3e−→FeFe3++3e−→Fe
B) Mg+Cl2→MgCl2Mg+Cl2​→MgCl2​
C) Cu+2e−→Cu2+Cu+2e−→Cu2+
D) H2+2e−→2H−H2​+2e−→2H−

Answer: C) Cu+2e−→Cu2+Cu+2e−→Cu2+

Explanation: Copper is losing electrons and increasing its oxidation state from 0 to +2, which is oxidation.

Question 33:

In a redox reaction, which of the following pairs are always oxidizing and reducing agents, respectively?
A) Fe3+Fe3+ and CuCu
B) AgAg and AuAu
C) Cl−Cl− and Br2Br2​
D) NaNa and MgMg

Answer: C) Cl−Cl− and Br2Br2​

Explanation: In this case, Cl−Cl− acts as a reducing agent, while Br2Br2​ acts as an oxidizing agent in the redox reaction.

Question 34:

Which of the following species is commonly used as an oxidizing agent in organic reactions?
A) H2O2H2​O2​
B) NaClNaCl
C) NaOHNaOH
D) H2H2​

Answer: A) H2O2H2​O2​

Explanation: Hydrogen peroxide is frequently used as an oxidizing agent in various organic reactions.

Question 35:

In the balanced reaction 2Fe+3Cl2→2FeCl32Fe+3Cl2​→2FeCl3​, which element is oxidized?
A) Cl
B) Fe
C) FeCl
D) None of the above

Answer: B) Fe

Explanation: Iron (Fe) is oxidized from 0 to +3 in FeCl3FeCl3​.

Question 36:

Which ion is reduced in the reaction 2MnO4−+5C2O42−+6H+→2Mn2++10CO2+3H2O2MnO4−​+5C2​O42−​+6H+→2Mn2++10CO2​+3H2​O?
A) MnO4−MnO4−​
B) C2O42−C2​O42−​
C) H+H+
D) CO2CO2​

Answer: A) MnO4−MnO4−​

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

Question 37:

What is the oxidation state of sulfur in H2SH2​S?
A) +2
B) -2
C) 0
D) +1

Answer: B) -2

Explanation: In hydrogen sulfide (H2SH2​S), sulfur has an oxidation state of -2.

Question 38:

Which of the following is a common oxidizing agent used in organic chemistry?
A) KMnO4KMnO4​
B) NaClNaCl
C) HClHCl
D) CaCO3CaCO3​

Answer: A) KMnO4KMnO4​

Explanation: Potassium permanganate (KMnO4KMnO4​) is widely used as an oxidizing agent in organic chemistry.

Question 39:

In the reaction 2H2+O2→2H2O2H2​+O2​→2H2​O, what is the oxidation state of oxygen in water?
A) -2
B) 0
C) +1
D) -1

Answer: A) -2

Explanation: In water (H2OH2​O), the oxidation state of oxygen is -2.

Question 40:

What is the primary role of a salt bridge in an electrochemical cell?
A) To provide a source of electrons.
B) To maintain charge balance.
C) To promote oxidation.
D) To prevent oxidation.

Answer: B) To maintain charge balance.

Explanation: A salt bridge allows the movement of ions, helping to maintain electrical neutrality in the half-cells.

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