JEE Main - Redox concepts oxidation numbers and balancing redox reactions Online Test (MCQ Quiz)

1. What is the oxidation number of sulfur in the sulfate ion (SO₄²⁻)?

A) +2 B) +4 C) +6 D) -2

2. In the reaction 2Na + Cl₂ → 2NaCl, what is the oxidation state of sodium in NaCl?

A) 0 B) +1 C) -1 D) +2

3. Which element is oxidized in the reaction: Zn + CuSO₄ → ZnSO₄ + Cu?

A) Zn B) Cu C) S D) O

4. What is the oxidation state of manganese in KMnO₄?

A) +2 B) +4 C) +6 D) +7

5. Identify the oxidizing agent in the reaction: 5Fe²⁺ + MnO₄⁻ + 8H⁺ → 5Fe³⁺ + Mn²⁺ + 4H₂O

A) Fe²⁺ B) MnO₄⁻ C) H⁺ D) Fe³⁺

6. What is the oxidation number of chlorine in HClO₄?

A) +1 B) +3 C) +5 D) +7

7. In a redox reaction, the substance that gains electrons is said to be:

A) Oxidized B) Reduced C) Catalyzed D) Neutralized

8. What is the oxidation state of phosphorus in P₄O₁₀?

A) +2 B) +4 C) +5 D) -3

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

A) Combustion of methane B) Neutralization of HCl by NaOH C) Rusting of iron D) Electrolysis of water

10. What is the sum of oxidation numbers of all atoms in K₂Cr₂O₇?

A) 0 B) +1 C) +2 D) +6

11. In the reaction 2H₂S + SO₂ → 3S + 2H₂O, what is oxidized?

A) H₂S B) SO₂ C) S D) H₂O

12. What is the oxidation state of nitrogen in NH₃?

A) +3 B) -3 C) 0 D) +1

13. Which species acts as a reducing agent in the reaction: 2KMnO₄ + 10FeSO₄ + 8H₂SO₄ → K₂SO₄ + 2MnSO₄ + 5Fe₂(SO₄)₃ + 8H₂O?

A) KMnO₄ B) FeSO₄ C) H₂SO₄ D) Fe₂(SO₄)₃

14. What is the oxidation number of oxygen in H₂O₂?

A) -1 B) -2 C) 0 D) +1

15. The process of gaining electrons is known as:

A) Oxidation B) Reduction C) Disproportionation D) Combustion

16. Balance the following redox reaction in acidic medium: Cr₂O₇²⁻ + SO₂ → Cr³⁺ + SO₄²⁻. What is the coefficient of SO₂?

A) 1 B) 2 C) 3 D) 4

17. What is the oxidation state of carbon in CO₂?

A) 0 B) +2 C) +4 D) -4

18. In which of the following compounds does manganese exhibit its highest oxidation state?

A) MnO₂ B) KMnO₄ C) Mn₂O₃ D) MnO

19. Which of the following is a characteristic of a reducing agent?

A) It causes oxidation B) It gains electrons C) Its oxidation number decreases D) It is always reduced

20. What is the oxidation number of chromium in CrO₅?

A) +5 B) +6 C) +8 D) +10

21. Balance the reaction: MnO₄⁻ + S²⁻ → Mn²⁺ + S (in acidic medium). What is the coefficient of S²⁻?

A) 1 B) 2 C) 3 D) 5

22. What is the oxidation state of chlorine in NaClO₃?

A) +1 B) +3 C) +5 D) -1

23. Which element is reduced in the reaction: 2Na + Cl₂ → 2NaCl?

A) Na B) Cl C) Both D) Neither

24. What is the oxidation number of sulfur in S₈?

A) 0 B) +1 C) -1 D) +2

25. In a redox reaction, the substance that loses electrons is said to be:

A) Oxidized B) Reduced C) Catalyzed D) Neutralized

26. Balance the following redox reaction in basic medium: ClO⁻ + Cr(OH)₃ → Cl⁻ + CrO₄²⁻. What is the coefficient of Cr(OH)₃?

A) 1 B) 2 C) 3 D) 4

27. What is the oxidation state of phosphorus in H₃PO₄?

A) +3 B) +5 C) +1 D) -3

28. Identify the reducing agent in the reaction: I₂ + 2S₂O₃²⁻ → 2I⁻ + S₄O₆²⁻

A) I₂ B) S₂O₃²⁻ C) I⁻ D) S₄O₆²⁻

29. What is the oxidation number of nitrogen in N₂O₅?

A) +5 B) +2 C) +1 D) 0

30. In the reaction: 2KClO₃ → 2KCl + 3O₂, what is oxidized?

A) K B) Cl C) O D) None

31. What is the oxidation state of iron in Fe₃O₄?

A) +2 B) +3 C) +8/3 D) +4

32. Balance the reaction: BrO₃⁻ + Br⁻ → Br₂ (in acidic medium). What is the coefficient of BrO₃⁻?

A) 1 B) 2 C) 3 D) 4

33. What is the oxidation state of sulfur in H₂S₂O₇ (oleum)?

A) +4 B) +5 C) +6 D) -2

34. Which of the following is an example of a disproportionation reaction?

A) Zn + CuSO₄ → ZnSO₄ + Cu B) 2H₂O₂ → 2H₂O + O₂ C) HCl + NaOH → NaCl + H₂O D) Fe + S → FeS

35. What is the oxidation number of oxygen in O₂F₂?

A) -1 B) -2 C) +1 D) +2

36. In the Haber process (N₂ + 3H₂ ⇌ 2NH₃), what is the oxidation state of nitrogen in NH₃?

A) 0 B) +1 C) -3 D) +3

37. Balance the reaction: C₂O₄²⁻ + MnO₄⁻ → CO₂ + Mn²⁺ (in acidic medium). What is the coefficient of MnO₄⁻?

A) 1 B) 2 C) 3 D) 5

38. What is the oxidation state of carbon in CH₄?

A) +4 B) -4 C) 0 D) +2

39. Which species is reduced in the reaction: 5H₂O₂ + 2MnO₄⁻ + 6H⁺ → 5O₂ + 2Mn²⁺ + 8H₂O?

A) H₂O₂ B) MnO₄⁻ C) H⁺ D) O₂

40. What is the oxidation number of phosphorus in PCl₃?

A) +3 B) +5 C) -3 D) 0

41. Which of the following is the most likely oxidation state of iodine in IF₅?

A) +1 B) +3 C) +5 D) -1

42. Balance the following redox reaction in basic medium: Ni(OH)₂ + N₂O₄ → Ni₂O₃ + NO₂⁻ + H₂O. What is the coefficient of N₂O₄?

A) 1 B) 2 C) 3 D) 4

43. What is the oxidation state of sulfur in Na₂S₂O₃ (sodium thiosulfate)?

A) +2 B) +2.5 C) +4 D) +6

44. In the reaction 2KMnO₄ + 16HCl → 2KCl + 2MnCl₂ + 5Cl₂ + 8H₂O, what is oxidized?

A) K B) Mn C) Cl (in HCl) D) H

45. What is the oxidation number of carbon in C₆H₁₂O₆ (glucose)?

A) 0 B) +1 C) -1 D) +2

46. Which of the following is a strong oxidizing agent?

A) SO₂ B) H₂S C) KMnO₄ D) CO

47. Balance the reaction: P₄ + OH⁻ → PH₃ + PO₄³⁻ (in basic medium). What is the coefficient of P₄?

A) 1 B) 2 C) 3 D) 4

48. What is the oxidation state of chlorine in ClF₃?

A) +3 B) +1 C) -1 D) +5

49. In the reaction 3NO₂ + H₂O → 2HNO₃ + NO, what is the oxidation state of nitrogen in NO?

A) +2 B) +4 C) +5 D) 0

50. Which element is reduced when H₂S reacts with Br₂ to form HBr and S?

A) H B) S C) Br D) None

Redox concepts oxidation numbers and balancing redox reactions - Online Test

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