Class 11 Chemistry Chapter 8 Redox Reactions MCQs

Class 11 chemistry MCQs with answers are provided here for chapter 8 Redox Reactions. These MCQs are based on the CBSE board curriculum and correspond to the most recent Class 11 chemistry syllabus. By practicing these Class 11 Multiple choice questions, students will be able to quickly review all of the ideas covered in the chapter and prepare for the Class 11 Annual examinations as well as other entrance exams such as NEET and JEE.

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Class 11 Redox Reactions MCQs

1. Which of the following is not a redox reaction?

(a) Burning of candle

(b) Rusting of iron

(c) Dissolving salt in water

(d) Dissolving Zinc in dil. H2SO4

Ans: (c)

Solution: Dissolving salt in water is not a redox reaction.

2. The oxidation number of Cr in Cr(CO)6 is —————–

(a) 0

(b) +2

(c) -2

(d) +6

Ans: (a)

Solution: CO is a neutral ligand whose charge is zero. In Cr(CO)6 complex, oxidation number of Cr is zero.

3. Which of the following is not a redox reaction?

(a) CaCO3 → CaO + CO2

(b) O2 + 2H2 → 2H2O

(c) Na + H2O → NaOH + 1/2H2

(d) MnCl3 → MnCl2 + 1/2 Cl2

Ans: (a)

Solution: CaCO3 → CaO + CO2

This is not a redox reaction because no element undergoes a change in oxidation number.

4. In the reaction

3Br2 + 6CO32- + 3H2O → 5Br + BrO3 + 6HCO3

(a) Bromine is oxidised and carbonate is reduced.

(b) Bromine is reduced and water is oxidised.

(c) Bromine is neither reduced nor oxidised.

(d) Bromine is both reduced and oxidised.

Ans: (d)

Solution: In this reaction, Br2 undergoes both decrease as well as increase in an oxidation number, it is both reduced and oxidised.

5. The most powerful oxidising agent among the following is:

(a) H2SO4

(b) H3BO3

(c) HPO3

(d) H3PO4

Ans: (a)

Solution: H2SO4 is the most powerful oxidising agent.

6. The oxidation number of Cr in K2Cr2O7 is:

(a) -6

(b) +6

(c) +2

(d) -2

Ans: (b)

Solution: In the K2Cr2O7 complex, let the oxidation number of Cr be x.

Then 2(+1) + 2(x) + 7 (-2) = 0 ⇒ 2x = +12 ⇒ x = +6

7. Consider the following reaction:

Zn + Cu2+ → Zn2+ + Cu

With reference to the above, which one of the following is the correct statement?

(a) Zn is reduced to Zn2+ ions.

(b) Zn is oxidised to Zn2+ ions.

(c) Zn2+ ions are oxidised to Zn.

(d) Cu2+ ions are oxidized to Cu.

Ans: (b)

Solution: Zn is oxidised to Zn2+ ions by releasing electrons.

8. Oxidation number of P in PO43-, of S in SO42- and that of Cr in Cr2O72- are respectively:

(a) +3, +6 and +5

(b) +5, +3 and +6

(c) +3, +6 and +6

(d) +5, +6 and +6

Ans: (d)

Solution: PO43- : x + 4 (-2) = -3 ⇒ x = +5

SO42- : x + 4 (-2) = -2 ⇒ x = +6

Cr2O72- : 2x + 7(-2) = -2 ⇒ x = +6

9. In the reaction:

2Ag + 2H2SO4 → Ag2SO4 + 2H2O + SO2

Sulphuric acid acts as:

(a) Oxidising agent

(b) Reducing agent

(c) Catalyst

(d) Acid as well as oxidant

Ans: (d)

Solution: Sulphuric acid acts as acid as well as oxidant.

10. Reduction never involves:

(a) gain of electrons

(b) decrease in oxidation number

(c) loss of electrons

(d) decrease in valency of electropositive component

Ans: (c)

Solution: Reduction never involves loss of electrons

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