NEET UG - Oxidation and reduction concepts, oxidation numbers, balancing redox reactions Online Test (MCQ Quiz)

1. Which process involves the loss of electrons?

A) Reduction B) Oxidation C) Neutralization D) Dissociation

2. In a chemical reaction, the gain of electrons is called:

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

3. What is the oxidation number of an element in its free and uncombined state?

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

4. The sum of oxidation numbers of all atoms in a neutral molecule is:

A) Always positive B) Always negative C) Zero D) Equal to the number of atoms

5. In the reaction $2Na + Cl_2 → 2NaCl$, what is the oxidation number of Sodium (Na)?

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

6. In the reaction $2Na + Cl_2 → 2NaCl$, what is the oxidation number of Chlorine (Cl)?

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

7. What is the oxidation number of Oxygen in most of its compounds?

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

8. What is the oxidation number of Hydrogen when bonded to non-metals?

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

9. What is the oxidation number of Hydrogen when bonded to metals?

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

10. What is the oxidation number of Fluorine in all its compounds?

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

11. In the polyatomic ion $SO_4^{2-}$, what is the oxidation number of Sulfur (S)?

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

12. In the compound $H_2O_2$ (hydrogen peroxide), what is the oxidation number of Oxygen?

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

13. The process of gaining oxygen or losing hydrogen is considered:

A) Reduction B) Oxidation C) Acid-base reaction D) Decomposition

14. The process of losing oxygen or gaining hydrogen is considered:

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

15. Which of the following is a reducing agent?

A) Oxygen B) Chlorine C) Hydrogen Sulfide ($H_2S$) D) Potassium Permanganate ($KMnO_4$)

16. Which of the following is an oxidizing agent?

A) Sulfur Dioxide ($SO_2$) B) Ammonia ($NH_3$) C) Potassium Dichromate ($K_2Cr_2O_7$) D) Sodium Chloride ($NaCl$)

17. In the reaction $Zn + CuSO_4 → ZnSO_4 + Cu$, Zinc is:

A) Oxidized B) Reduced C) Neither oxidized nor reduced D) An oxidizing agent

18. In the reaction $Zn + CuSO_4 → ZnSO_4 + Cu$, Copper is:

A) Oxidized B) Reduced C) Neither oxidized nor reduced D) A reducing agent

19. To balance a redox reaction using the oxidation number method, the change in oxidation numbers on both sides must be:

A) Equal B) Opposite C) Zero D) Doubled

20. In acidic medium, to balance a redox reaction, which species is added to balance oxygen atoms?

A) $H^+$ B) $OH^-$ C) $H_2O$ D) Electrons

21. In acidic medium, to balance a redox reaction, which species is added to balance hydrogen atoms?

A) $H^+$ B) $OH^-$ C) $H_2O$ D) Electrons

22. In basic medium, to balance a redox reaction, which species is added to balance oxygen atoms?

A) $H^+$ B) $OH^-$ C) $H_2O$ D) Electrons

23. In basic medium, to balance a redox reaction, which species is added to balance hydrogen atoms?

A) $H^+$ B) $OH^-$ C) $H_2O$ D) Electrons

24. Balancing redox reactions in basic medium typically involves adding $OH^-$ and $H_2O$ to balance oxygen and hydrogen atoms respectively, and then:

A) Adding $H^+$ to both sides B) Adding electrons to balance charge C) Multiplying by a stoichiometric coefficient D) Ignoring the charge balance

25. Which of the following is an example of intramolecular redox reaction?

A) $Zn + CuSO_4 → ZnSO_4 + Cu$ B) $2H_2 + O_2 → 2H_2O$ C) $KClO_3 → KCl + O_2$ D) $HCl + NaOH → NaCl + H_2O$

26. Which of the following is an example of disproportionation reaction?

A) $Cl_2 + 2KI → 2KCl + I_2$ B) $2Na + Cl_2 → 2NaCl$ C) $2H_2O_2 → 2H_2O + O_2$ D) $Zn + 2HCl → ZnCl_2 + H_2$

27. In the reaction $MnO_4^- + 5Fe^{2+} + 8H^+ → Mn^{2+} + 5Fe^{3+} + 4H_2O$, the oxidation number of Manganese changes from:

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

28. In the reaction $MnO_4^- + 5Fe^{2+} + 8H^+ → Mn^{2+} + 5Fe^{3+} + 4H_2O$, the oxidation number of Iron changes from:

A) +3 to +2 B) +2 to +3 C) 0 to +2 D) +2 to 0

29. The species that gets oxidized in a redox reaction is the:

A) Oxidizing agent B) Reducing agent C) Both oxidizing and reducing agent D) Spectator ion

30. The species that gets reduced in a redox reaction is the:

A) Oxidizing agent B) Reducing agent C) Both oxidizing and reducing agent D) Catalyst

31. In the reaction $I_2 + S_2O_3^{2-} → 2I^- + S_4O_6^{2-}$, Iodine ($I_2$) is:

A) Oxidized B) Reduced C) Neither oxidized nor reduced D) Both oxidized and reduced

32. In the reaction $I_2 + S_2O_3^{2-} → 2I^- + S_4O_6^{2-}$, Thiosulfate ion ($S_2O_3^{2-}$) is:

A) Oxidized B) Reduced C) Neither oxidized nor reduced D) Both oxidized and reduced

33. What is the oxidation number of Carbon in $CO_2$?

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

34. What is the oxidation number of Carbon in $CH_4$?

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

35. What is the oxidation number of Chromium in $K_2Cr_2O_7$?

A) +6 B) +7 C) +3 D) +2

36. What is the oxidation number of Manganese in $KMnO_4$?

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

37. What is the oxidation number of Nitrogen in $NH_3$?

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

38. What is the oxidation number of Nitrogen in $NO_2$?

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

39. What is the oxidation number of Phosphorus in $P_4O_{10}$?

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

40. Which of the following reactions is NOT a redox reaction?

A) $H_2 + Cl_2 → 2HCl$ B) $2KClO_3 → 2KCl + 3O_2$ C) $HCl + NaOH → NaCl + H_2O$ D) $Zn + CuSO_4 → ZnSO_4 + Cu$

41. In the reaction $SO_2 + 2H_2S → 3S + 2H_2O$, Sulfur dioxide ($SO_2$) acts as:

A) An oxidizing agent B) A reducing agent C) Both oxidizing and reducing agent D) Neither

42. In the reaction $SO_2 + 2H_2S → 3S + 2H_2O$, Hydrogen sulfide ($H_2S$) acts as:

A) An oxidizing agent B) A reducing agent C) Both oxidizing and reducing agent D) Neither

43. Which element is oxidized in the reaction $2KMnO_4 + 16HCl → 2KCl + 2MnCl_2 + 5Cl_2 + 8H_2O$?

A) Potassium (K) B) Manganese (Mn) C) Chlorine (Cl) D) Oxygen (O)

44. Which element is reduced in the reaction $2KMnO_4 + 16HCl → 2KCl + 2MnCl_2 + 5Cl_2 + 8H_2O$?

A) Potassium (K) B) Manganese (Mn) C) Chlorine (Cl) D) Hydrogen (H)

45. The half-reaction representing oxidation is:

A) Gain of electrons B) Loss of electrons C) Gain of protons D) Loss of protons

46. The half-reaction representing reduction is:

A) Loss of electrons B) Gain of electrons C) Loss of neutrons D) Gain of neutrons

47. In balancing a redox reaction by the ion-electron method, electrons are added to balance:

A) Mass B) Charge C) Number of atoms D) The overall reaction

48. The oxidation number of an element in an ion is equal to:

A) Zero B) The charge of the ion C) The number of atoms in the ion D) The number of electrons lost

49. Which statement is correct regarding redox reactions?

A) Oxidation and reduction occur independently. B) Oxidation can occur without reduction. C) Reduction can occur without oxidation. D) Oxidation and reduction occur simultaneously.

50. In the reaction $C + O_2 → CO_2$, Carbon is oxidized from an oxidation state of 0 to:

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

Oxidation and reduction concepts, oxidation numbers, balancing redox reactions - Online Test

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