{"id":12763,"date":"2025-09-22T13:59:06","date_gmt":"2025-09-22T12:59:06","guid":{"rendered":"https:\/\/mcqsadda.com\/?p=12763"},"modified":"2025-11-03T09:12:02","modified_gmt":"2025-11-03T09:12:02","slug":"oxidation-and-reduction-top-100-mcqs-with-answer-and-explanation","status":"publish","type":"post","link":"https:\/\/mcqsadda.com\/index.php\/2025\/09\/22\/oxidation-and-reduction-top-100-mcqs-with-answer-and-explanation\/","title":{"rendered":"Oxidation and reduction Top 100 MCQs With Answer and Explanation"},"content":{"rendered":"\n

1. Oxidation is defined as:<\/mark><\/strong>
A) Gain of electrons
B) Loss of electrons
C) Gain of protons
D) Loss of neutrons
Answer:<\/strong> B
Explanation:<\/strong> Oxidation is the process in which an atom, ion, or molecule loses electrons.<\/p>\n\n\n\n

2. Reduction is defined as:<\/mark><\/strong>
A) Gain of electrons
B) Loss of electrons
C) Gain of protons
D) Loss of neutrons
Answer:<\/strong> A
Explanation:<\/strong> Reduction involves the gain of electrons.<\/p>\n\n\n\n

3. In the reaction , sodium is:<\/mark><\/strong>
A) Oxidized
B) Reduced
C) Both oxidized and reduced
D) Neither
Answer:<\/strong> A
Explanation:<\/strong> Sodium loses an electron \u2192 oxidation.<\/p>\n\n\n\n

4. In the reaction , chlorine is:<\/mark><\/strong>
A) Oxidized
B) Reduced
C) Both
D) Neither
Answer:<\/strong> B
Explanation:<\/strong> Chlorine gains an electron \u2192 reduction.<\/p>\n\n\n\n

5. An oxidizing agent:<\/mark><\/strong>
A) Gains electrons
B) Loses electrons
C) Both
D) None
Answer:<\/strong> A
Explanation:<\/strong> Oxidizing agents oxidize other substances and are themselves reduced (gain electrons).<\/p>\n\n\n\n

6. A reducing agent:<\/mark><\/strong>
A) Gains electrons
B) Loses electrons
C) Both
D) None
Answer:<\/strong> B
Explanation:<\/strong> Reducing agents reduce other substances and are themselves oxidized (lose electrons).<\/p>\n\n\n\n

7. The oxidation number of oxygen in H\u2082O\u2082 is:<\/mark><\/strong>
A) -2
B) -1
C) 0
D) +1
Answer:<\/strong> B
Explanation:<\/strong> In peroxide (H\u2082O\u2082), oxygen has oxidation number -1.<\/p>\n\n\n\n

8. The oxidation number of hydrogen in NaH is:<\/mark><\/strong>
A) +1
B) 0
C) -1
D) +2
Answer:<\/strong> C
Explanation:<\/strong> In hydrides (NaH), hydrogen is -1.<\/p>\n\n\n\n

9. Oxidation involves:<\/mark><\/strong>
A) Increase in oxidation number
B) Decrease in oxidation number
C) No change in oxidation number
D) Variable
Answer:<\/strong> A
Explanation:<\/strong> Losing electrons increases the oxidation number.<\/p>\n\n\n\n

10. Reduction involves:<\/mark><\/strong>
A) Increase in oxidation number
B) Decrease in oxidation number
C) No change
D) Variable
Answer:<\/strong> B
Explanation:<\/strong> Gaining electrons decreases the oxidation number.<\/p>\n\n\n\n

11. In , Fe is:<\/mark><\/strong>
A) Oxidized
B) Reduced
C) Both
D) Neither
Answer:<\/strong> B
Explanation:<\/strong> Fe\u00b3\u207a in Fe\u2082O\u2083 gains electrons \u2192 reduction.<\/p>\n\n\n\n

12. In the same reaction, CO is:<\/mark><\/strong>
A) Oxidized
B) Reduced
C) Both
D) Neither
Answer:<\/strong> A
Explanation:<\/strong> CO loses electrons \u2192 oxidation to CO\u2082.<\/p>\n\n\n\n

13. In , oxygen is:<\/mark><\/strong>
A) Oxidized
B) Reduced
C) Both
D) Neither
Answer:<\/strong> B
Explanation:<\/strong> Oxygen gains electrons \u2192 reduction.<\/p>\n\n\n\n

14. In , hydrogen is:<\/mark><\/strong>
A) Oxidized
B) Reduced
C) Both
D) Neither
Answer:<\/strong> A
Explanation:<\/strong> Hydrogen loses electrons \u2192 oxidation.<\/p>\n\n\n\n

15. Oxidation number of sulfur in H\u2082SO\u2084 is:<\/mark><\/strong>
A) +4
B) +6
C) +2
D) -2
Answer:<\/strong> B
Explanation:<\/strong> Calculation: 2(H\u207a) + S + 4(O\u00b2\u207b) = 0 \u2192 S = +6.<\/p>\n\n\n\n

16. Oxidation number of nitrogen in NH\u2084\u207a is:<\/mark><\/strong>
A) -3
B) +1
C) 0
D) +5
Answer:<\/strong> A
Explanation:<\/strong> H\u207a = +1, sum of charges = +1 \u2192 N = -3.<\/p>\n\n\n\n

17. Oxidation number of Cl in ClO\u2084\u207b is:<\/mark><\/strong>
A) +7
B) +5
C) +3
D) +1
Answer:<\/strong> A
Explanation:<\/strong> O = -2, 4\u00d7(-2) + Cl = -1 \u2192 Cl = +7.<\/p>\n\n\n\n

18. In , Zn is:<\/mark><\/strong>
A) Oxidized
B) Reduced
C) Both
D) Neither
Answer:<\/strong> A
Explanation:<\/strong> Zn loses 2 electrons \u2192 oxidized.<\/p>\n\n\n\n

19. In the same reaction, Cu\u00b2\u207a is:
<\/mark><\/strong>A) Oxidized
B) Reduced
C) Both
D) Neither
Answer:<\/strong> B
Explanation:<\/strong> Cu\u00b2\u207a gains 2 electrons \u2192 reduced.<\/p>\n\n\n\n

20. Which of the following is a good oxidizing agent?<\/mark><\/strong>
A) KMnO\u2084
B) H\u2082
C) Zn
D) Na
Answer:<\/strong> A
Explanation:<\/strong> KMnO\u2084 in acidic medium accepts electrons \u2192 oxidizes other substances.<\/p>\n\n\n\n

21. Which of the following is a good reducing agent?<\/mark><\/strong>
A) NaBH\u2084
B) O\u2082
C) H\u2082O\u2082
D) KMnO\u2084
Answer:<\/strong> A
Explanation:<\/strong> NaBH\u2084 donates electrons \u2192 reduces other substances.<\/p>\n\n\n\n

22. Oxidation number of carbon in CO\u2082 is:<\/mark><\/strong>
A) +2
B) +4
C) -2
D) 0
Answer:<\/strong> B
Explanation:<\/strong> O = -2, 2\u00d7(-2) + C = 0 \u2192 C = +4.<\/p>\n\n\n\n

23. Oxidation number of carbon in CH\u2084 is:<\/mark><\/strong>
A) +4
B) -4
C) 0
D) +2
Answer:<\/strong> B
Explanation:<\/strong> H = +1, 4\u00d7(+1) + C = 0 \u2192 C = -4.<\/p>\n\n\n\n

24. In disproportionation reactions:<\/mark><\/strong>
A) Same species is both oxidized and reduced
B) Two different species react
C) Only oxidation occurs
D) Only reduction occurs
Answer:<\/strong> A
Explanation:<\/strong> E.g., , O in H\u2082O\u2082 is both reduced and oxidized.<\/p>\n\n\n\n

25. Which element can show disproportionation?<\/mark><\/strong>
A) Chlorine in hypochlorite solution
B) Sodium
C) Magnesium
D) Helium
Answer:<\/strong> A
Explanation:<\/strong> Cl in NaOCl is partially oxidized to ClO\u2083\u207b and partially reduced to Cl\u207b.<\/p>\n\n\n\n

26. In the reaction , the number of electrons transferred per Fe atom is:<\/mark><\/strong>
A) 1
B) 2
C) 3
D) 0
Answer:<\/strong> B
Explanation:<\/strong> Fe \u2192 Fe\u00b2\u207a + 2e\u207b, so 2 electrons are transferred per atom.<\/p>\n\n\n\n

27. Oxidation number change in for Mn is:<\/mark><\/strong>
A) +7 \u2192 +2
B) +2 \u2192 +7
C) +6 \u2192 +2
D) +7 \u2192 +6
Answer:<\/strong> A
Explanation:<\/strong> Mn goes from +7 in MnO\u2084\u207b to +2 in Mn\u00b2\u207a \u2192 gain of 5 electrons.<\/p>\n\n\n\n

28. In the same reaction, Fe\u00b2\u207a is:<\/mark><\/strong>
A) Oxidized to Fe\u00b3\u207a
B) Reduced to Fe\u2070
C) Both
D) Neither
Answer:<\/strong> A
Explanation:<\/strong> Fe\u00b2\u207a loses one electron \u2192 Fe\u00b3\u207a \u2192 oxidized.<\/p>\n\n\n\n

29. Redox reaction is a reaction where:<\/mark><\/strong>
A) Only oxidation occurs
B) Only reduction occurs
C) Both oxidation and reduction occur simultaneously
D) No electron transfer occurs
Answer:<\/strong> C
Explanation:<\/strong> A redox reaction involves simultaneous oxidation and reduction.<\/p>\n\n\n\n

30. Which of the following is an example of a redox reaction?<\/mark><\/strong>
A) Zn + 2HCl \u2192 ZnCl\u2082 + H\u2082
B) HCl + NaOH \u2192 NaCl + H\u2082O
C) BaCl\u2082 + Na\u2082SO\u2084 \u2192 BaSO\u2084 + 2NaCl
D) AgNO\u2083 + NaCl \u2192 AgCl + NaNO\u2083
Answer:<\/strong> A
Explanation:<\/strong> Zn \u2192 Zn\u00b2\u207a (oxidation), H\u207a \u2192 H\u2082 (reduction).<\/p>\n\n\n\n

31. In balancing redox reactions by oxidation number method, first step is:<\/mark><\/strong>
A) Identify oxidizing and reducing agents
B) Balance all atoms except H and O
C) Balance electrons lost and gained
D) Multiply to equalize electrons
Answer:<\/strong> A
Explanation:<\/strong> First step is to identify which species are oxidized and reduced.<\/p>\n\n\n\n

32. In acidic medium, H\u2082O is used to:<\/mark><\/strong>
A) Balance H atoms
B) Balance O atoms
C) Balance electrons
D) None
Answer:<\/strong> B
Explanation:<\/strong> Water is added to balance oxygen atoms in acidic medium.<\/p>\n\n\n\n

33. In basic medium, OH\u207b is used to:<\/mark><\/strong>
A) Balance O atoms
B) Balance H atoms
C) Balance electrons
D) Both A & B
Answer:<\/strong> D
Explanation:<\/strong> OH\u207b balances H and O in basic medium reactions.<\/p>\n\n\n\n

34. The number of electrons transferred in is:<\/mark><\/strong>
A) 3
B) 6
C) 2
D) 4
Answer:<\/strong> B
Explanation:<\/strong> Cr \u2192 Cr\u00b3\u207a loses 3e\u207b per atom, 2 atoms \u2192 6 electrons.<\/p>\n\n\n\n

35. Oxidation number of Cr in Cr\u2082O\u2087\u00b2\u207b is:<\/mark><\/strong>
A) +3
B) +6
C) +4
D) +2
Answer:<\/strong> B
Explanation:<\/strong> O = -2, 7\u00d7(-2) + 2\u00d7Cr = -2 \u2192 Cr = +6.<\/p>\n\n\n\n

36. In the reaction , Cl is:<\/mark><\/strong>
A) Both oxidized and reduced
B) Only oxidized
C) Only reduced
D) Neither
Answer:<\/strong> A
Explanation:<\/strong> Disproportionation: Cl in Cl\u2082 (0) \u2192 Cl\u207b (-1, reduced) and Cl\u207a (+1 in ClO\u207b, oxidized).<\/p>\n\n\n\n

37. Strongest oxidizing agent in acidic medium:<\/mark><\/strong>
A) KMnO\u2084
B) Na\u2082SO\u2084
C) NaCl
D) H\u2082O
Answer:<\/strong> A
Explanation:<\/strong> KMnO\u2084 has Mn\u2077\u207a \u2192 easily reduced \u2192 strong oxidizing agent.<\/p>\n\n\n\n

38. Strongest reducing agent among: H\u2082, Na, CO, C<\/mark><\/strong>
Answer:<\/strong> Na
Explanation:<\/strong> Sodium readily loses electron \u2192 strong reducing agent.<\/p>\n\n\n\n

39. Standard electrode potential (E\u00b0) measures:<\/mark><\/strong>
A) Oxidizing power
B) Reducing power
C) Both
D) Neither
Answer:<\/strong> A
Explanation:<\/strong> Positive E\u00b0 \u2192 good oxidizing agent; negative E\u00b0 \u2192 good reducing agent.<\/p>\n\n\n\n

40. Which metal can displace Zn from ZnSO\u2084 solution?<\/mark><\/strong>
A) Cu
B) Mg
C) Ag
D) Au
Answer:<\/strong> B
Explanation:<\/strong> Mg is more reactive (higher in electrochemical series) \u2192 displaces Zn\u00b2\u207a.<\/p>\n\n\n\n

41. Electrochemical series arranges elements according to:<\/mark><\/strong>
A) Atomic number
B) Electronegativity
C) Standard reduction potential
D) Density
Answer:<\/strong> C
Explanation:<\/strong> Electrochemical series ranks elements by standard reduction potential (E\u00b0).<\/p>\n\n\n\n

42. In the reaction , Cl\u2082 is:<\/mark><\/strong>
A) Oxidizing agent
B) Reducing agent
C) Both
D) Neither
Answer:<\/strong> A
Explanation:<\/strong> Cl\u2082 gains electrons \u2192 reduced, acts as oxidizing agent.<\/p>\n\n\n\n

43. In , Cu is:<\/mark><\/strong>
A) Oxidized
B) Reduced
C) Both
D) Neither
Answer:<\/strong> A
Explanation:<\/strong> Cu \u2192 Cu\u00b2\u207a loses 2 electrons \u2192 oxidation.<\/p>\n\n\n\n

44. In the same reaction, Ag\u207a is:<\/mark><\/strong>
A) Oxidized
B) Reduced
C) Both
D) Neither
Answer:<\/strong> B
Explanation:<\/strong> Ag\u207a gains electrons \u2192 reduction.<\/p>\n\n\n\n

45. In corrosion of iron, Fe reacts with O\u2082 and H\u2082O to form:<\/mark><\/strong>
A) FeO
B) Fe\u2082O\u2083\u00b7xH\u2082O
C) FeCl\u2083
D) FeS
Answer:<\/strong> B
Explanation:<\/strong> Rust is hydrated ferric oxide \u2192 Fe\u2082O\u2083\u00b7xH\u2082O.<\/p>\n\n\n\n

46. Redox titration uses:<\/mark><\/strong>
A) KMnO\u2084 and oxalic acid
B) HCl and NaOH
C) BaCl\u2082 and Na\u2082SO\u2084
D) NaCl and AgNO\u2083
Answer:<\/strong> A
Explanation:<\/strong> KMnO\u2084 oxidizes oxalic acid in redox titration.<\/p>\n\n\n\n

47. In , H\u2082O\u2082 acts as:<\/mark><\/strong>
A) Oxidizing agent
B) Reducing agent
C) Both
D) Neither
Answer:<\/strong> C
Explanation:<\/strong> H\u2082O\u2082 disproportionates \u2192 gets oxidized and reduced simultaneously.<\/p>\n\n\n\n

48. Disproportionation of Cl\u2082 in water forms:<\/mark><\/strong>
A) HCl and HClO
B) HCl only
C) HClO only
D) Cl\u2082O
Answer:<\/strong> A
Explanation:<\/strong> Cl\u2082 + H\u2082O \u2192 HCl + HClO.<\/p>\n\n\n\n

49. Oxidation number of Mn in MnO\u2084\u00b2\u207b is:<\/mark><\/strong>
A) +6
B) +7
C) +4
D) +2
Answer:<\/strong> A
Explanation:<\/strong> Mn + 4(-2) = -2 \u2192 Mn = +6.<\/p>\n\n\n\n

50. The reducing agent in is:<\/mark><\/strong>
A) Zn
B) H\u207a
C) Cl\u207b
D) H\u2082
Answer:<\/strong> A
Explanation:<\/strong> Zn loses electrons \u2192 reduces H\u207a to H\u2082 \u2192 Zn is reducing agent.<\/p>\n\n\n\n

51. Electrolysis is:<\/mark><\/strong>
A) A redox reaction occurring spontaneously
B) Non-spontaneous redox reaction driven by electricity
C) Oxidation only
D) Reduction only
Answer:<\/strong> B
Explanation:<\/strong> Electrolysis uses external electrical energy to drive non-spontaneous redox reactions.<\/p>\n\n\n\n

52. In electrolysis, the electrode where oxidation occurs is called:<\/mark><\/strong>
A) Cathode
B) Anode
C) Electrolyte
D) Salt bridge
Answer:<\/strong> B
Explanation:<\/strong> Oxidation occurs at the anode (positive in electrolysis).<\/p>\n\n\n\n

53. In electrolysis, the electrode where reduction occurs is called:<\/mark><\/strong>
A) Cathode
B) Anode
C) Electrolyte
D) Salt bridge
Answer:<\/strong> A
Explanation:<\/strong> Reduction occurs at the cathode (negative in electrolysis).<\/p>\n\n\n\n

54. During electrolysis of molten NaCl, the products at cathode and anode are:<\/mark><\/strong>
A) Na at cathode, Cl\u2082 at anode
B) Cl\u2082 at cathode, Na at anode
C) NaCl at cathode, Na at anode
D) Na at both electrodes
Answer:<\/strong> A
Explanation:<\/strong> Na\u207a reduced at cathode \u2192 Na; Cl\u207b oxidized at anode \u2192 Cl\u2082.<\/p>\n\n\n\n

55. In aqueous electrolysis, water can compete with ions because:<\/mark><\/strong>
A) Water is inert
B) Water can also be oxidized\/reduced
C) Water is a good conductor
D) None
Answer:<\/strong> B
Explanation:<\/strong> H\u2082O can be reduced to H\u2082 or oxidized to O\u2082 depending on ion reduction potential.<\/p>\n\n\n\n

56. In electrolysis of CuSO\u2084 with copper electrodes, the cathode:<\/mark><\/strong>
A) Loses Cu
B) Gains Cu
C) Loses O\u2082
D) Gains H\u2082
Answer:<\/strong> B
Explanation:<\/strong> Cu\u00b2\u207a ions are reduced \u2192 deposited on cathode.<\/p>\n\n\n\n

57. Galvanic cell is:<\/mark><\/strong>
A) A non-spontaneous redox reaction
B) A spontaneous redox reaction producing electricity
C) Oxidation only
D) Reduction only
Answer:<\/strong> B
Explanation:<\/strong> Galvanic\/voltaic cells convert chemical energy into electrical energy spontaneously.<\/p>\n\n\n\n

58. In a Daniell cell, the anode reaction is:<\/mark><\/strong>
A) Zn \u2192 Zn\u00b2\u207a + 2e\u207b
B) Cu\u00b2\u207a + 2e\u207b \u2192 Cu
C) Cu \u2192 Cu\u00b2\u207a + 2e\u207b
D) Zn\u00b2\u207a + 2e\u207b \u2192 Zn
Answer:<\/strong> A
Explanation:<\/strong> Zn is oxidized at the anode \u2192 Zn\u00b2\u207a + 2e\u207b.<\/p>\n\n\n\n

59. In a Daniell cell, the cathode reaction is:<\/mark>
<\/strong>A) Zn \u2192 Zn\u00b2\u207a + 2e\u207b
B) Cu\u00b2\u207a + 2e\u207b \u2192 Cu
C) Cu \u2192 Cu\u00b2\u207a + 2e\u207b
D) Zn\u00b2\u207a + 2e\u207b \u2192 Zn
Answer:<\/strong> B
Explanation:<\/strong> Cu\u00b2\u207a ions are reduced at the cathode \u2192 Cu metal.<\/p>\n\n\n\n

60. The salt bridge in a galvanic cell:<\/mark><\/strong>
A) Prevents mixing of solutions
B) Maintains electrical neutrality
C) Conducts electrons directly
D) Produces ions
Answer:<\/strong> B
Explanation:<\/strong> Salt bridge allows ion flow to maintain charge balance.<\/p>\n\n\n\n

61. Standard electrode potential (E\u00b0) is measured under:<\/mark><\/strong>
A) 1 atm pressure, 25\u00b0C, 1 M solution
B) Any condition
C) High temperature only
D) Low pressure only
Answer:<\/strong> A
Explanation:<\/strong> Standard conditions: 25\u00b0C, 1 atm, 1 M solution.<\/p>\n\n\n\n

62. Element with higher E\u00b0 is:<\/mark><\/strong>
A) Stronger reducing agent
B) Stronger oxidizing agent
C) Less reactive
D) Inert
Answer:<\/strong> B
Explanation:<\/strong> Higher E\u00b0 \u2192 greater tendency to gain electrons \u2192 strong oxidizing agent.<\/p>\n\n\n\n

63. Which metal can reduce Ag\u207a from solution?<\/mark><\/strong>
A) Zn
B) Cu
C) Hg
D) Au
Answer:<\/strong> A
Explanation:<\/strong> Zn has lower E\u00b0 \u2192 stronger reducing agent than Ag\u207a.<\/p>\n\n\n\n

64. In electroplating, the object to be plated is:<\/mark><\/strong>
A) Anode
B) Cathode
C) Electrolyte
D) Salt bridge
Answer:<\/strong> B
Explanation:<\/strong> Object to be plated is cathode \u2192 receives metal ions.<\/p>\n\n\n\n

65. Electroplating prevents:<\/mark><\/strong>
A) Oxidation
B) Corrosion
C) Both
D) Neither
Answer:<\/strong> C
Explanation:<\/strong> Coating of metal protects surface from corrosion and oxidation.<\/p>\n\n\n\n

66. Lead storage battery is:<\/mark><\/strong>
A) Primary cell
B) Secondary cell
C) Fuel cell
D) None
Answer:<\/strong> B
Explanation:<\/strong> Lead-acid battery can be recharged \u2192 secondary cell.<\/p>\n\n\n\n

67. In lead storage battery, the anode during discharge:<\/mark><\/strong>
A) Pb \u2192 PbSO\u2084 + 2e\u207b
B) PbO\u2082 + 4H\u207a + SO\u2084\u00b2\u207b + 2e\u207b \u2192 PbSO\u2084 + 2H\u2082O
C) Pb\u00b2\u207a + 2e\u207b \u2192 Pb
D) None
Answer:<\/strong> A
Explanation:<\/strong> Pb anode oxidized to PbSO\u2084 during discharge.<\/p>\n\n\n\n

68. In lead storage battery, cathode during discharge:<\/mark><\/strong>
A) Pb \u2192 PbSO\u2084
B) PbO\u2082 reduced \u2192 PbSO\u2084
C) Pb\u00b2\u207a \u2192 Pb
D) None
Answer:<\/strong> B
Explanation:<\/strong> PbO\u2082 reduced \u2192 PbSO\u2084.<\/p>\n\n\n\n

69. Dry cell is:<\/mark><\/strong>
A) Primary cell
B) Secondary cell
C) Fuel cell
D) Electrolytic cell
Answer:<\/strong> A
Explanation:<\/strong> Dry cells are non-rechargeable \u2192 primary cells.<\/p>\n\n\n\n

70. In molten NaCl electrolysis, Cl\u207b ions migrate to:<\/mark><\/strong>
A) Cathode
B) Anode
C) Electrolyte
D) Salt bridge
Answer:<\/strong> B
Explanation:<\/strong> Cl\u207b is oxidized at anode \u2192 Cl\u2082 gas.<\/p>\n\n\n\n

71. In molten NaCl electrolysis, Na\u207a ions migrate to:<\/mark><\/strong>
A) Cathode
B) Anode
C) Electrolyte
D) Salt bridge
Answer:<\/strong> A
Explanation:<\/strong> Na\u207a is reduced at cathode \u2192 Na metal.<\/p>\n\n\n\n

72. The cell in which chemical energy is converted to electrical energy spontaneously is:<\/mark><\/strong>
A) Galvanic cell
B) Electrolytic cell
C) Fuel cell
D) Dry cell
Answer:<\/strong> A
Explanation:<\/strong> Galvanic cell produces electricity from spontaneous redox reactions.<\/p>\n\n\n\n

73. Which of the following can act as both oxidizing and reducing agent?<\/mark><\/strong>
A) H\u2082O\u2082
B) Zn
C) Cu
D) HCl
Answer:<\/strong> A
Explanation:<\/strong> H\u2082O\u2082 disproportionates \u2192 reduced to H\u2082O and oxidized to O\u2082.<\/p>\n\n\n\n

74. Oxidizing power of halogens decreases down the group because:<\/mark><\/strong>
A) Electronegativity decreases
B) Atomic size increases
C) Both A & B
D) None
Answer:<\/strong> C
Explanation:<\/strong> Lower electronegativity and larger size \u2192 weaker oxidizing ability.<\/p>\n\n\n\n

75. Redox reaction is widely used in:<\/mark><\/strong>
A) Metal extraction
B) Electroplating
C) Batteries
D) All of these
Answer:<\/strong> D
Explanation:<\/strong> Redox reactions are fundamental in industry, electrochemistry, and energy storage.<\/p>\n\n\n\n

76. Corrosion of iron occurs faster in:<\/mark><\/strong>
A) Dry air
B) Moist air
C) Pure oxygen
D) Pure nitrogen
Answer:<\/strong> B
Explanation:<\/strong> Water acts as an electrolyte \u2192 promotes redox reaction \u2192 rust formation.<\/p>\n\n\n\n

77. The main product of iron corrosion is:<\/mark><\/strong>
A) FeO
B) Fe\u2082O\u2083\u00b7xH\u2082O
C) FeCl\u2083
D) FeS
Answer:<\/strong> B
Explanation:<\/strong> Rust is hydrated ferric oxide (Fe\u2082O\u2083\u00b7xH\u2082O).<\/p>\n\n\n\n

78. In corrosion, the anode is:<\/mark><\/strong>
A) Fe
B) O\u2082
C) H\u2082O
D) Fe\u00b2\u207a
Answer:<\/strong> A
Explanation:<\/strong> Fe loses electrons \u2192 oxidation occurs at anodic sites.<\/p>\n\n\n\n

79. Cathodic protection prevents corrosion by:<\/mark><\/strong>
A) Applying electric current
B) Coating with metal like Zn
C) Both A & B
D) Using water
Answer:<\/strong> C
Explanation:<\/strong> Cathodic protection reduces oxidation of Fe \u2192 via sacrificial anode or impressed current.<\/p>\n\n\n\n

80. In sacrificial protection, the anode is:<\/mark><\/strong>
A) More reactive metal than iron
B) Less reactive metal than iron
C) Iron itself
D) Non-metal
Answer:<\/strong> A
Explanation:<\/strong> Metal like Zn or Mg corrodes instead of iron \u2192 sacrificial protection.<\/p>\n\n\n\n

81. In fuel cells, chemical energy is converted into electricity:<\/mark><\/strong>
A) Spontaneously
B) Non-spontaneously
C) Only with external battery
D) Only at high temperature
Answer:<\/strong> A
Explanation:<\/strong> Fuel cells use spontaneous redox reactions (e.g., H\u2082 + O\u2082 \u2192 H\u2082O).<\/p>\n\n\n\n

82. In hydrogen fuel cell, the anode reaction is:<\/mark><\/strong>
A) H\u2082 \u2192 2H\u207a + 2e\u207b
B) O\u2082 + 4H\u207a + 4e\u207b \u2192 2H\u2082O
C) H\u2082 + O\u2082 \u2192 H\u2082O
D) H\u207a + e\u207b \u2192 H
Answer:<\/strong> A
Explanation:<\/strong> Hydrogen is oxidized at anode \u2192 electrons flow to cathode.<\/p>\n\n\n\n

83. In hydrogen fuel cell, cathode reaction is:<\/mark><\/strong>
A) H\u2082 \u2192 2H\u207a + 2e\u207b
B) O\u2082 + 4H\u207a + 4e\u207b \u2192 2H\u2082O
C) H\u207a + e\u207b \u2192 H
D) H\u2082 + O\u2082 \u2192 H\u2082O
Answer:<\/strong> B
Explanation:<\/strong> Oxygen is reduced at cathode to form water.<\/p>\n\n\n\n

84. Standard potential of SHE (standard hydrogen electrode) is:
<\/mark><\/strong>A) 0 V
B) +1 V
C) -1 V
D) 0.5 V
Answer:<\/strong> A
Explanation:<\/strong> By definition, standard electrode potential of SHE = 0 V.<\/p>\n\n\n\n

85. In organic redox, KMnO\u2084 oxidizes:<\/mark><\/strong>
A) Alcohols to aldehydes\/carboxylic acids
B) Alkanes to alkenes
C) Aromatics to halides
D) None
Answer:<\/strong> A
Explanation:<\/strong> KMnO\u2084 is a strong oxidizing agent \u2192 oxidizes primary alcohols to carboxylic acids.<\/p>\n\n\n\n

86. Oxidation of ethanol with acidified K\u2082Cr\u2082O\u2087 gives:<\/mark><\/strong>
A) CH\u2083CHO (acetaldehyde) or CH\u2083COOH (acetic acid)
B) CH\u2084
C) C\u2082H\u2086
D) C\u2082H\u2085Cl
Answer:<\/strong> A
Explanation:<\/strong> Primary alcohol \u2192 aldehyde \u2192 carboxylic acid on complete oxidation.<\/p>\n\n\n\n

87. Redox titration can be done using:<\/mark><\/strong>
A) KMnO\u2084
B) Iodine
C) Both A & B
D) NaCl
Answer:<\/strong> C
Explanation:<\/strong> Both KMnO\u2084 and I\u2082 are commonly used in redox titrations.<\/p>\n\n\n\n

88. Oxidation number of C in HCOOH is:
<\/mark><\/strong>A) -1
B) +2
C) 0
D) +1
Answer:<\/strong> B
Explanation:<\/strong> H = +1, O = -2, sum = 0 \u2192 C = +2.<\/p>\n\n\n\n

89. Chlorine water reacts with KI to form:<\/mark><\/strong>
A) I\u2082 + HCl
B) Cl\u2082 + KI
C) HCl + KClO
D) I\u2082 + KCl + H\u2082O
Answer:<\/strong> D
Explanation:<\/strong> Cl\u2082 oxidizes I\u207b \u2192 I\u2082, also forms KCl and H\u2082O.<\/p>\n\n\n\n

90. Oxidation number of nitrogen in HNO\u2083 is:<\/mark><\/strong>
A) +5
B) +3
C) +2
D) 0
Answer:<\/strong> A
Explanation:<\/strong> H = +1, 3O = -6, N = +5 to balance charge \u2192 HNO\u2083 neutral.<\/p>\n\n\n\n

91. Which metal is used as sacrificial anode for iron protection?<\/mark><\/strong>
A) Zn
B) Cu
C) Fe
D) Pb
Answer:<\/strong> A
Explanation:<\/strong> Zn is more reactive \u2192 corrodes instead of iron.<\/p>\n\n\n\n

92. In contact process, SO\u2082 is oxidized to SO\u2083 using:<\/mark><\/strong>
A) V\u2082O\u2085
B) H\u2082SO\u2084
C) O\u2082
D) Fe
Answer:<\/strong> A
Explanation:<\/strong> V\u2082O\u2085 acts as catalyst for oxidation \u2192 redox reaction.<\/p>\n\n\n\n

93. In electrorefining of copper, anode is:<\/mark><\/strong>
A) Impure Cu
B) Pure Cu
C) Graphite
D) Zn
Answer:<\/strong> A
Explanation:<\/strong> Impure Cu oxidized \u2192 dissolves as Cu\u00b2\u207a \u2192 deposited on cathode.<\/p>\n\n\n\n

94. Cathode in electrorefining of copper:<\/mark><\/strong>
A) Impure Cu
B) Pure Cu
C) Graphite
D) Zn
Answer:<\/strong> B
Explanation:<\/strong> Cu\u00b2\u207a reduced at cathode \u2192 pure Cu metal deposited.<\/p>\n\n\n\n

95. In voltaic cell, electrons flow from:<\/mark><\/strong>
A) Anode \u2192 Cathode
B) Cathode \u2192 Anode
C) Salt bridge \u2192 Cathode
D) Electrolyte \u2192 Anode
Answer:<\/strong> A
Explanation:<\/strong> Electrons flow from oxidized species (anode) \u2192 reduced species (cathode).<\/p>\n\n\n\n

96. Which is strongest oxidizing agent among halogens?<\/mark><\/strong>
A) F\u2082
B) Cl\u2082
C) Br\u2082
D) I\u2082
Answer:<\/strong> A
Explanation:<\/strong> Fluorine has highest electronegativity \u2192 strongest oxidizing agent.<\/p>\n\n\n\n

97. In corrosion, moisture accelerates rusting because:<\/mark><\/strong>
A) Acts as electrolyte
B) Dissolves CO\u2082
C) Both A & B
D) None
Answer:<\/strong> C
Explanation:<\/strong> Moisture + CO\u2082 \u2192 weak carbonic acid \u2192 accelerates iron oxidation.<\/p>\n\n\n\n

98. Redox reactions are important in:<\/mark><\/strong>
A) Bleaching
B) Disinfection
C) Metallurgy
D) All of these
Answer:<\/strong> D
Explanation:<\/strong> Redox reactions are central in chemical industry, health, and metal extraction.<\/p>\n\n\n\n

99. Oxidation number of Cr in K\u2082Cr\u2082O\u2087 is:<\/mark><\/strong>
A) +6
B) +3
C) +2
D) +4
Answer:<\/strong> A
Explanation:<\/strong> K = +1, O = -2 \u2192 Cr = +6.<\/p>\n\n\n\n

100. Oxidizing agent in redox reaction is always:<\/mark><\/strong>
A) Reduced
B) Oxidized
C) Neither
D) Both
Answer:<\/strong> A
Explanation:<\/strong> Oxidizing agent gains electrons \u2192 gets reduced.<\/p>\n","protected":false},"excerpt":{"rendered":"

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