Questions on Oxidation and Reduction

These Redox Reaction Balancing Questions are prepared by our LiveMCQs team for NEET. These questions are based on the chapter on Redox Reactions. Preparation of these questions has been taken from various books including NCERT, Previous year’s question papers, and model papers. So these Questions on Oxidation Number Class 11 cover all the topics of Redox Reactions. These MCQs are very helpful in your preparation for the National Eligibility cum Entrance Test-UG (NEET) and JEE mains. We have provided these questions in PDF format which you can Download by clicking the link “Redox Reaction JEE Mains Questions” provide below.

Questions on Oxidation and Reduction

1. Identify the correct statements with reference to the given reaction

P4 + 3OH–+ 3H2O → PH3+ 3H2PO2–

(A) Phosphorus is undergoing reduction only.

(B) Phosphorus is undergoing oxidation only.

(C) Phosphorus is undergoing oxidation as well as reduction.

(D) Hydrogen is undergoing neither oxidation nor reduction.

Answer: C, D

2. The exhibition of various oxidation states by an element is also related to the outer orbital electronic configuration of its atom. Atom(s) having which of the following outermost electronic configurations will exhibit more than one oxidation state in its compounds.

(A) 3s1

(B) 3d1 4s2

(C) 3d2 4s2

(D) 3s2 3p3

Answer: C, D

3. Which of the following statement(s) is/are not true about the following decomposition reaction.

2KClO3 → 2KCl + 3O2

(A) Potassium is undergoing oxidation

(B) Chlorine is undergoing oxidation

(C) Oxygen is reduced

(D) None of the species is undergoing oxidation or reduction

Answer: A, D

4. The largest oxidation number exhibited by an element depends on its outer electronic configuration. With which of the following outer electronic configurations the element will exhibit the largest oxidation number?

(A) 3d1 4s2

(B) 3d3 4s2

(C) 3d5 4s1

(D) 3d5 4s2

Answer: 3d5 4s2

5. Which of the following arrangements represent increasing oxidation number of the central atom?

(A) CrO2- , CIO-3, CrO2-4 , MnO-4

(B) CIO-3, CrO2-4 , MnO-4 , CrO-2

(C) CrO2+4 , MnO-4 , CrO-2 , CIO3-

(D) CrO24-, MnO4- , CrO2- , CIO3-

Answer: CrO2- , CIO-3, CrO2-4 , MnO-4

6. In which of the following compounds, an element exhibits two different oxidation states.

(A) NH2OH7

(B) NH4NO3

(C) N2H4

(D) N3H

Answer: NH4NO3

7. The oxidation number of an element in a compound is evaluated on the basis of certain rules. Which of the following rules is not correct in this respect?

(A) The oxidation number of hydrogen is always +1.

(B) The algebraic sum of all the oxidation numbers in a compound is zero.

(C) An element in the free or the uncombined state bears oxidation number zero.

(D) In all its compounds, the oxidation number of fluorine is – 1

Answer: The oxidation number of hydrogen is always +1.

8. The oxidation number of an element in a compound is evaluated on the basis of certain rules. Which of the following rules is not correct in this respect?

(A) The oxidation number of hydrogen is always +1.

(B) The algebraic sum of all the oxidation numbers in a compound is zero.

(C) An element in the free or the uncombined state bears oxidation number zero.

(D) In all its compounds, the oxidation number of fluorine is -1.

Answer: The oxidation number of hydrogen is always +1.

9. In which of the following compounds, an element exhibits two different oxidation states.

(A) NH2OH

(B) NH4NO3

(C) N2H4

(D) N3H

Answer: NH4NO3

10. The largest oxidation number exhibited by an element depends on its outer electronic configuration. With which of the following outer electronic configurations the element will exhibit largest oxidation number?

(A) 3d14s2

(B) 3d2 4s2

(C) 3d54s1

(D) 3d54s2

Answer: 3d54s2

11. Identify disproportionation reaction

(A) CH4 + 202 → C02 + 2H20

(B) CH4 + 4C12 → CC14 + 4HCl

(C) 2F2 + 20H–→2F– + OF2 + H20

(D) 2N02 + 20H– → N02 + NO–3 + H20

Answer: 2N02 + 20H– → N02 + NO–3 + H20

12. The oxidation number of an element in a compound is evaluated on the basis of certain rules. Which of the following rules is not correct in this respect?

(A) The oxidation number of hydrogen is always +1.

(B) The algebraic sum of all the oxidation numbers in a compound is zero.

(C) An element in the free or the uncombined state bears oxidation number zero.

(D) In all its compounds, the oxidation number of fluorine is – 1.

Answer: The oxidation number of hydrogen is always +1.

13. In which of the following compounds, an element exhibits two different oxidation states.

(A) NH2OH

(B) NH4NO3

(C) N2H4

(D) N3H

Answer: N2H4

14. The colourless solution of silver nitrate slowly turns blue on adding copper chips to it because of

(A) Dissolution of Copper

(B) Oxidation of Ag+ → Ag

(C) Reduction of Cu2+ ions

(D) Oxidation of Cu atoms.

Answer: Oxidation of Cu atoms.

15. The oxidation number of Xe in BaXeO6 is

(A) 8

(B) 6

(C) 4

(D) 10

Answer: 10

16. The oxidation process involves

(A) Increase in oxidation number

(B) Decrease in oxidation number

(C) No change in oxidation number

(D) None of the above

Answer: Increase in oxidation number

17. The oxidation number of Mn is maximum in

(A) MnO2

(B) K2MnO4

(C) Mn3O4

(D) KMnO4.

Answer: KMnO4

18. One mole of N2H4 loses ten moles of electrons to form a new compound A. Assuming that all the nitrogen appears in the new compound, what is the oxidation state of nitrogen in A? (There is no change in the oxidation state of hydrogen.)

(A) -1

(B) -3

(C) +3

(D) +5

Answer: +3

19. Which of the following reactions does not involve either oxidation or reduction?

(A) VO2+ → V2O3

(B) Na → Na+

(C) CrO2-4 → Cr2O2-7

(D) Zn2+ →Zn

Answer: CrO2-4 → Cr2O2-7

20. Which of the following processes does not involve oxidation of iron?

(A) Formation of Fe(CO)5 from Fe.

(B) Liberation of H2 from steam by iron at high temperature.

(C) Rusting of iron sheets.

(D) Decolourisation of blue CuSO4 solution by iron.

Answer: Formation of Fe(CO)5 from Fe.

21. The oxidation state of Cr in Cr (CO)6 is

(A) 0

(B) 2

(C) 2

(D) 6

Answer: 0

22. One mole of N2H4 loses ten moles of electrons to form a new compound A. Assuming that all the nitrogen appears in the new compound, what is the oxidation state of nitrogen in A? (There is no change in the oxidation state of hydrogen.

(A) -1

(B) -3

(C) +3

(D) +5

Answer: +3

23. Which of the following processes does not involve either oxidation or reduction?

(A) Formation of slaked lime from quick lime

(B) Heating Mercuric Oxide

(C) Formation of Manganese Chloride from Manganese oxide

(D) Formation of Zinc from Zinc blende

Answer: Formation of slaked lime from quick lime

24. The tendency of an electrode to lose electrons is known as

(A) Electrode Potential

(B) Reduction Potential

(C) Oxidation Potential

(D) E.M.F.

Answer: Oxidation Potential

25. What is known as Autooxidation?

(A) Formation of H2O by the oxidation of H2O2.

(B) Formation of H2O2 by the oxidation of H2O.

(C) Both (1) and (2) are true

(D) None of the above

Answer: Formation of H2O2 by the oxidation of H2O.

26. The oxidation number of Cl in Cl2O7 is

(A) + 7

(B) + 5

(C) + 3

(D) – 7

Answer: + 7

27. In which of the following complex, the oxidation number of Fe is +1?

(A) Fe4[Fe(CN)6]3

(B) [Fe(H2O)5NO]SO4

(C) [FeBr4]

(D) [Fe(H2O)6]2-

Answer: [Fe(H2O)5NO]SO4

28. Find the oxidation state of I in H4IO6

(A) +7

(B) +5

(C) +1

(D) -1

Answer: +7

29. H2O2 changes Cr2O72- ion to CrO5 in an acidic medium, the oxidation state of Cr in CrO5 is

(A) +6

(B) +5

(C) -10

(D) +3

Answer: +6

30. One mole of ferrous oxalate requires____ moles of MnO4 to get oxidised completely in an acidic medium

(A) 0.6 moles

(B) 0.4 moles

(C) 0.2 moles

(D) 7.5 moles

Answer: 0.4 moles

31. Which of the compounds can exist together?

(A) HgCl2, SnCl2

(B) FeCl3, KI

(C) FeCl3, SnCl2

(D) FeCl2, SnCl2

Answer: FeCl2, SnCl2

32. In the following questions, a statement of assertion (A) followed by a statement of the reason (R) is given. Choose the correct option out of the choices given below each question.

Assertion (A): Redox couple is the combination of the oxidised and reduced form of a substance involved in an oxidation or reduction half cell.

Reason (R) : In the representation E° Fe3+/fe2+and E°cu2+/cu , Fe3+ / Fe2+ and Cu2+ are redox couples.

(A) Both A and R are true and R is the correct explanation of A.

(B) Both A and R are true but R is not the correct explanation of A.

(C) A is true but R is false.

(D) Both A and R are false

Answer: Both A and R are true but R is not the correct explanation of A.

33. Assertion (A): The decomposition of hydrogen peroxide to form water and oxygen is an example of a disproportionation reaction.

Reason (R): The oxygen of peroxide is in –1 oxidation state and it is converted to zero oxidation state in O2 and –2 oxidation state in H2O.

(A) Both A and R are true and R is the correct explanation of A.

(B) Both A and R are true but R is not the correct explanation of A.

(C) A is true but R is false.

(D) Both A and R are false.

Answer: Both A and R are true and R is the correct explanation of A.

34. Assertion (A): In the reaction between potassium permanganate and potassium iodide, permanganate ions act as an oxidising agent.

Reason (R): Oxidation state of manganese changes from +2 to +7 during the reaction.

(A) Both A and R are true and R is the correct explanation of A.

(B) Both A and R are true but R is not the correct explanation of A.

(C) A is true but R is false.

(D) Both A and R are false.

Answer: A is true but R is false.

35. Find the redox reaction

(A) In the atmosphere, O3 from O2 by lighting

(B) The reaction of H2SO4 with NaOH

(C) Both oxidation and reduction reaction

(D) Evaporation of water

Answer: Both oxidation and reduction reaction

36. During a reaction of oxalic acid, potassium chlorate and sulphuric acid, the oxidation number of which of the element undergoes a maximum change

(A) H

(B) S

(C) C

(D) Cl

Answer: Cl

37. A standard reduction electrode potentials of four metals are A = -0.250 V, B = -0.140 V, C = -0.126 V, D = -0.402 V. The metal that displaces A from its aqueous solution is:

(A) A

(B) B

(C) C

(D) D

Answer: D

38. Metals generally react with dilute acids to produce hydrogen gas. Which one of the following metals does not react with dilute hydrochloric acid?

(A) Copper

(B) Magnesium

(C) Iron

(D) Silver

Answer: Magnesium

39. What is n-factor?

(A) Equal to product of Number of moles of electrons when Lost or gained by one mole of reductant or oxidant

(B) When Number of moles of electrons Lost or gained by one mole of reductant or oxidant is not same.

(C) Equal to Number of moles of electrons Lost or gained by one mole of reductant or oxidant

(D) None of the above

Answer: Equal to Number of moles of electrons Lost or gained by one mole of reductant or oxidant

30. KMnO4 reacts with oxalic acid according to the equation 2MnO4 + 5C2O42- + 16H+ → 2Mn2+ +10CO2 + 8H2O Here 20 mL of 0.1 M KMnO4 is equivalent to

(A) 50 mL of 0.5 M C2H2O4

(B) 20 mL of 0.1 M C2H2O4

(C) 20 mL of 0.5 M C2H2O4

(D) 50 mL of 0.1 M C2H2O4

Answer: 50 mL of 0.1 M C2H2O4

31. The number of moles of KMnO4 reduced by one mole of KI in alkaline medium is

(A) One

(B) Two

(C) Five

(D) One fifth.

Answer: Two

32. How many millilitres of 0.5 M H2SO4 are needed to dissolve 0.5 g of copper (II)carbonate?

(A) 6.01

(B) 4.5

(C) 8.1

(D) 11.1

Answer: 8.1

33. If equal volumes of 1M KMnO4 and 1M K2Cr2O7 solutions are allowed to oxidize Fe2+ in acidic medium. The amount of iron oxidized will be:

(A) More with KMnO2

(B) More with K2Cr2O7

(C) Equal with both oxidising agents

(D) Cannot be determined

Answer: More with K2Cr2O7

34. Which among the following is the strongest oxidising agent?

(A) H2O2

(B) O3

(C) K2Cr2O7

(D) KMnO4

Answer: O3

35. Which among the following compounds is the most reducing compound?

(A) H2S

(B) HNO2

(C) SnCl2

(D) H2SO3

Answer: H2S

36. H2SO4 acts as a strong oxidising agent. In which of the reaction, is it not acting as an oxidising agent?

(A) C + 2H2SO→ CO2 + 2SO2 + 2H2O

(B) CaF2 + 2H2SO→ CaSO4 + 2HF

(C) S + 2H2SO→ 3SO2 + H2O

(D) Cu + 2H2SO→ CuSO4 + SO2 + 2H2O

Answer: CaF2 + 2H2SO→ CaSO4 + 2HF

37. Assertion (A): Among halogens, fluorine is the best oxidant.

Reason (R): Fluorine is the most electronegative atom.

(A) Both A and R are true and R is the correct explanation of A.

(B) Both A and R are true but R is not the correct explanation of A.

(C) A is true but R is false.

(D) Both A and R are false.

Answer: Both A and R are true but R is not the correct explanation of A.

38. Which of the following electrodes will act as anodes, when connected to Standard Hydrogen Electrode?

(A) Al/Al2+ -E\degree = –1.66

(B) Fe/Fe2+ -E\degree = – 0.44

(C) Cu/Cu2+ -E\degree= + 0.34

(D) F2 (g)/2F- (aq) -E\degree= + 2.87

Answer: A, B

39. Identify the correct statement (s) with the following reaction:

Zn + 2HCl → ZnCl2 + H2

(A) Zinc is acting as an oxidant

(B) Chlorine is acting as a reductant

(C) Hydrogen ion is acting as an oxidant

(D) Zinc is acting as a reductant

Answer: C, D

40. Which of the following elements does not show disproportionation tendency?

(A) Cl

(B) Br

(C) F

(D) I

Answer: F

41. Identify disproportionation reaction

(A) CH4 + 2O2→ CO2 + 2H2O

(B) CH4 + 4Cl2→ CCl4 + 4HCl

(C) 2F2 + 2OH-→ 2F- + OF2 + H2O

(D) 2NO2 + 2OH–→ NO2- + NO3- + H2O

Answer: 2NO2 + 2OH–→ NO2- + NO3- + H2O

42. Using the standard electrode potential, find out the pair between which redox reaction is not feasible.

E°Values: Fe3+/ Fe2+ = +0.77; I2/I- = +0.54;

Cu2+/ Cu = -0.34; Ag+ /Ag = + 0.80 V

(A) Fe3+ and I-

(B) Ag+ and Cu

(C) Fe3+ and Cu

(D) Ag and Fe3+

Answer: Ag and Fe3+

43. Eᶱvalues of some redox couples is given below. Based on these values choose the correct option.

Eᶱ values: Br2/Br–= + 1.90; Ag+/Ag(s) = + 0.80

Cu2+/Cu(s) = + 0.34; I2(s)/I– = + 0.54

(A) Cu will reduce Br–

(B) Cu will reduce Ag

(C) Cu will reduce I–

(D) Cu will reduce Br2

Answer: Cu will reduce Br2

44. The more positive the value of Eᶱ, the greater is the tendency of the species to get reduced. Using the standard electrode potential of redox couples given below to find out which of the following is the strongest oxidising agent. Eᶱ Values: Fe3+/Fe2+ = + 0.77; I2(s)/I– = + 0.54;

Cu2+/Cu = + 0.34; Ag+/Ag = + 0.80V

(A) Fe3+

(B) I2(s)

(C) Cu2+

(D) Ag

Answer: Ag

45. Which of the following is not an example of redox reaction?

(A) CuO + H2→ Cu + H2O

(B) Fe2O3 + 3CO → 2Fe + 3CO2

(C) 2K + F2→ 2KF

(D) BaCl2 + H2SO4→ BaSO4 + 2HCl

Answer: BaCl2 + H2SO4→ BaSO4 + 2HCl

46. Identify disproportionation reaction

(A) CH4 + 2O2 → CO2 + 2H2O

(B) CH4 + 4Cl2→ CCl4 + 4HCl

(C) 2F2 + 2OH → 2F – + OF2 + H2O

(D) 2NO2 + 2OH ⎯→ NO2 + NO3 + H2O

Answer: 2NO2 + 2OH ⎯→ NO2 + NO3 + H2O

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