1. Oxidation involves:
A) Gain of electrons
B) Loss of electrons
C) Gain of protons
D) None of these
Answer: B
Explanation: Oxidation is the process of loss of electrons from an atom or ion.
2. Reduction involves:
A) Loss of electrons
B) Gain of electrons
C) Gain of oxygen
D) None of these
Answer: B
Explanation: Reduction is the gain of electrons by an atom, ion, or molecule.
3. Which of the following represents oxidation?
A) Fe → Fe²⁺ + 2e⁻
B) Cl₂ + 2e⁻ → 2Cl⁻
C) Cu²⁺ + 2e⁻ → Cu
D) H₂ + Cl₂ → 2HCl
Answer: A
Explanation: Iron loses two electrons—thus it is oxidized.
4. Which of the following represents reduction?
A) Zn → Zn²⁺ + 2e⁻
B) Cu²⁺ + 2e⁻ → Cu
C) Fe → Fe³⁺ + 3e⁻
D) O₂ → 2O
Answer: B
Explanation: Copper ion gains electrons and gets reduced.
5. In a redox reaction, the oxidizing agent:
A) Gets oxidized
B) Gets reduced
C) Loses electrons
D) Remains unchanged
Answer: B
Explanation: The oxidizing agent causes oxidation of another substance and itself gets reduced.
6. The reducing agent:
A) Causes reduction
B) Is reduced itself
C) Gains electrons
D) Is oxidized itself
Answer: D
Explanation: The reducing agent donates electrons, gets oxidized, and causes reduction.
7. Which of the following is both oxidized and reduced in the same reaction?
A) H₂O₂
B) O₂
C) H₂
D) Cl₂
Answer: A
Explanation: In its decomposition, H₂O₂ acts as both oxidizing and reducing agent.
8. In the reaction
Zn + CuSO₄ → ZnSO₄ + Cu,
which is the oxidizing agent?
A) Zn
B) Cu²⁺
C) SO₄²⁻
D) Cu
Answer: B
Explanation: Cu²⁺ accepts electrons (is reduced), so it is the oxidizing agent.
9. In the same reaction, the reducing agent is:
A) Zn
B) Cu²⁺
C) Cu
D) SO₄²⁻
Answer: A
Explanation: Zn loses electrons and is oxidized—hence the reducing agent.
10. Oxidation number of oxygen in H₂O₂ is:
A) -2
B) -1
C) 0
D) +1
Answer: B
Explanation: Each oxygen in H₂O₂ has oxidation state -1.
11. The oxidation number of sulfur in H₂SO₄ is:
A) +4
B) +6
C) +2
D) +3
Answer: B
Explanation: 2(+1)+x+4(−2)=0⇒x=+62(+1) + x + 4(-2) = 0 \Rightarrow x = +62(+1)+x+4(−2)=0⇒x=+6
12. Which of the following has zero oxidation number?
A) H₂
B) NaCl
C) H₂O
D) NaOH
Answer: A
Explanation: Free elements have zero oxidation number.
13. Which is not an oxidizing agent?
A) KMnO₄
B) K₂Cr₂O₇
C) Na₂S
D) H₂O₂
Answer: C
Explanation: Na₂S acts as a reducing agent.
14. The oxidation state of nitrogen in NH₃ is:
A) +3
B) -3
C) 0
D) +5
Answer: B
Explanation: x+3(+1)=0⇒x=−3x + 3(+1) = 0 \Rightarrow x = -3x+3(+1)=0⇒x=−3
15. Which element undergoes oxidation in the reaction
2Mg + O₂ → 2MgO?
A) O
B) Mg
C) Both
D) None
Answer: B
Explanation: Mg loses electrons and is oxidized.
16. Which undergoes reduction in above reaction?
A) O₂
B) Mg
C) Both
D) None
Answer: A
Explanation: O₂ gains electrons forming oxide ion.
17. The oxidation number of chlorine in NaClO₃ is:
A) +1
B) +3
C) +5
D) +7
Answer: C
Explanation: +1+x+3(−2)=0⇒x=+5+1 + x + 3(-2) = 0 \Rightarrow x = +5+1+x+3(−2)=0⇒x=+5
18. Disproportionation reaction means:
A) Oxidation and reduction of same element
B) Only oxidation occurs
C) Only reduction occurs
D) None
Answer: A
Explanation: In disproportionation, the same element is both oxidized and reduced.
19. Example of disproportionation reaction is:
A) 2H₂O₂ → 2H₂O + O₂
B) Zn + CuSO₄ → ZnSO₄ + Cu
C) 2Mg + O₂ → 2MgO
D) H₂ + Cl₂ → 2HCl
Answer: A
Explanation: Oxygen in H₂O₂ changes from -1 to 0 and -2.
20. Oxidation number of Mn in KMnO₄ is:
A) +4
B) +6
C) +7
D) +2
Answer: C
Explanation: +1+x+4(−2)=0⇒x=+7+1 + x + 4(-2) = 0 \Rightarrow x = +7+1+x+4(−2)=0⇒x=+7
21. Oxidation number of Cr in K₂Cr₂O₇ is:
A) +3
B) +6
C) +2
D) +7
Answer: B
Explanation: 2(+1)+2x+7(−2)=0⇒x=+62(+1) + 2x + 7(-2) = 0 \Rightarrow x = +62(+1)+2x+7(−2)=0⇒x=+6
22. Oxidation number of Fe in Fe₂O₃ is:
A) +2
B) +3
C) +1
D) +6
Answer: B
Explanation: 2x+3(−2)=0⇒x=+32x + 3(-2) = 0 \Rightarrow x = +32x+3(−2)=0⇒x=+3
23. Which of the following is a reducing agent?
A) H₂
B) O₂
C) Cl₂
D) KMnO₄
Answer: A
Explanation: H₂ donates electrons and hence acts as a reducing agent.
24. Which is an oxidizing agent?
A) CO
B) H₂S
C) O₃
D) SO₂
Answer: C
Explanation: Ozone (O₃) readily releases oxygen and acts as a strong oxidizing agent.
25. The oxidation number of N in HNO₃ is:
A) +3
B) +5
C) +2
D) +4
Answer: B
Explanation: +1+x+3(−2)=0⇒x=+5+1 + x + 3(-2) = 0 \Rightarrow x = +5+1+x+3(−2)=0⇒x=+5
26. In Fe + CuSO₄ → FeSO₄ + Cu, Fe is:
A) Oxidized
B) Reduced
C) Unchanged
D) Catalyst
Answer: A
Explanation: Fe → Fe²⁺ + 2e⁻ (oxidation).
27. The oxidation number of S in SO₂ is:
A) +2
B) +4
C) +6
D) 0
Answer: B
Explanation: x+2(−2)=0⇒x=+4x + 2(-2) = 0 \Rightarrow x = +4x+2(−2)=0⇒x=+4
28. Which of the following involves reduction?
A) Addition of oxygen
B) Addition of hydrogen
C) Loss of hydrogen
D) None
Answer: B
Explanation: Reduction can also be defined as gain of hydrogen.
29. Which of the following is a redox reaction?
A) NaCl + AgNO₃ → AgCl + NaNO₃
B) 2Mg + O₂ → 2MgO
C) BaCl₂ + H₂SO₄ → BaSO₄ + 2HCl
D) NaOH + HCl → NaCl + H₂O
Answer: B
Explanation: There is transfer of electrons — oxidation of Mg and reduction of O₂.
30. Oxidation number of Cl in HClO₄ is:
A) +1
B) +3
C) +5
D) +7
Answer: D
Explanation: +1+x+4(−2)=0⇒x=+7+1 + x + 4(-2) = 0 \Rightarrow x = +7+1+x+4(−2)=0⇒x=+7
31. Oxidation number of Mn in MnO₂ is:
A) +2
B) +4
C) +6
D) +7
Answer: B
Explanation: x+2(−2)=0⇒x=+4x + 2(-2) = 0 \Rightarrow x = +4x+2(−2)=0⇒x=+4
32. Which of the following is a disproportionation reaction?
A) 3Cl₂ + 6NaOH → 5NaCl + NaClO₃ + 3H₂O
B) Zn + CuSO₄ → ZnSO₄ + Cu
C) Mg + O₂ → MgO
D) H₂ + Cl₂ → 2HCl
Answer: A
Explanation: Chlorine undergoes both oxidation and reduction.
33. In the reaction
Cl₂ + 2KI → 2KCl + I₂,
oxidizing agent is:
A) KI
B) Cl₂
C) K⁺
D) I₂
Answer: B
Explanation: Cl₂ gains electrons and oxidizes iodide ions.
34. In the same reaction, reducing agent is:
A) KI
B) Cl₂
C) K⁺
D) I₂
Answer: A
Explanation: I⁻ loses electrons and is oxidized.
35. Oxidation number of oxygen in OF₂ is:
A) -2
B) -1
C) 0
D) +2
Answer: D
Explanation: x+2(−1)=0⇒x=+2x + 2(-1) = 0 \Rightarrow x = +2x+2(−1)=0⇒x=+2
36. In the reaction
Zn + 2HCl → ZnCl₂ + H₂,
hydrogen is:
A) Oxidized
B) Reduced
C) Unchanged
D) Catalyst
Answer: B
Explanation: H⁺ gains electrons → H₂ (reduction).
37. The oxidation number of carbon in CO₂ is:
A) +4
B) +2
C) 0
D) -4
Answer: A
Explanation: x+2(−2)=0⇒x=+4x + 2(-2) = 0 \Rightarrow x = +4x+2(−2)=0⇒x=+4
38. The oxidation number of C in CH₄ is:
A) -4
B) +4
C) -2
D) +2
Answer: A
Explanation: x+4(+1)=0⇒x=−4x + 4(+1) = 0 \Rightarrow x = -4x+4(+1)=0⇒x=−4
39. In the reaction
2H₂ + O₂ → 2H₂O,
oxidizing agent is:
A) H₂
B) O₂
C) H₂O
D) None
Answer: B
Explanation: O₂ gains electrons (reduced), thus oxidizing agent.
40. Reducing agent in the same reaction is:
A) H₂
B) O₂
C) H₂O
D) None
Answer: A
Explanation: H₂ is oxidized, hence reducing agent.
41. The oxidation number of nitrogen in N₂O is:
A) +1
B) +2
C) +3
D) +4
Answer: A
Explanation: 2x+(−2)=0⇒x=+12x + (-2) = 0 \Rightarrow x = +12x+(−2)=0⇒x=+1
42. Oxidation number of N in NH₄⁺ is:
A) -3
B) +3
C) -4
D) -2
Answer: A
Explanation: x+4(+1)=+1⇒x=−3x + 4(+1) = +1 \Rightarrow x = -3x+4(+1)=+1⇒x=−3
43. Oxidation number of Cl in NaOCl is:
A) +1
B) -1
C) +3
D) +5
Answer: A
Explanation: +1+x+(−2)=0⇒x=+1+1 + x + (-2) = 0 \Rightarrow x = +1+1+x+(−2)=0⇒x=+1
44. Oxidation number of P in H₃PO₄ is:
A) +3
B) +5
C) +4
D) +2
Answer: B
Explanation: 3(+1)+x+4(−2)=0⇒x=+53(+1) + x + 4(-2) = 0 \Rightarrow x = +53(+1)+x+4(−2)=0⇒x=+5
45. Which is the oxidizing agent in the reaction
Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag?
A) Cu
B) Ag⁺
C) NO₃⁻
D) Ag
Answer: B
Explanation: Ag⁺ gains electrons (reduced).
46. Reducing agent in the above reaction is:
A) Cu
B) Ag⁺
C) NO₃⁻
D) Ag
Answer: A
Explanation: Cu is oxidized to Cu²⁺, acts as reducing agent.
47. Oxidation number of S in H₂S is:
A) -2
B) +2
C) 0
D) +4
Answer: A
Explanation: 2(+1)+x=0⇒x=−22(+1) + x = 0 \Rightarrow x = -22(+1)+x=0⇒x=−2
48. Which of the following is an example of oxidation?
A) Addition of oxygen
B) Addition of hydrogen
C) Gain of electrons
D) None
Answer: A
Explanation: Oxidation also means addition of oxygen.
49. Which species is oxidized in reaction:
Zn + H₂SO₄ → ZnSO₄ + H₂ ?
A) Zn
B) H₂
C) H⁺
D) SO₄²⁻
Answer: A
Explanation: Zn → Zn²⁺ (oxidation).
50. Oxidation number of Fe in Fe₃O₄ is:
A) +2
B) +3
C) Average +2.67
D) +1
Answer: C
Explanation: Fe₃O₄ = FeO·Fe₂O₃ → average = (2 + 2×3)/3 = +2.67
51. Redox reaction involves:
A) Transfer of protons
B) Transfer of electrons
C) Transfer of ions
D) None
Answer: B
Explanation: Redox reaction is based on electron transfer.
52. Oxidation number of S in Na₂SO₄ is:
A) +4
B) +6
C) +2
D) +3
Answer: B
Explanation: 2(+1)+x+4(−2)=0⇒x=+62(+1) + x + 4(-2) = 0 \Rightarrow x = +62(+1)+x+4(−2)=0⇒x=+6
53. Oxidation number of Cl in ClO₂ is:
A) +1
B) +3
C) +4
D) +5
Answer: C
Explanation: x+2(−2)=0⇒x=+4x + 2(-2) = 0 \Rightarrow x = +4x+2(−2)=0⇒x=+4
54. The oxidation number of oxygen in O₂F₂ is:
A) -1
B) 0
C) +1
D) +2
Answer: C
Explanation: 2x+2(−1)=0⇒x=+12x + 2(-1) = 0 \Rightarrow x = +12x+2(−1)=0⇒x=+1
55. Oxidation number of S in SO₃²⁻ is:
A) +4
B) +6
C) +2
D) 0
Answer: A
Explanation: x+3(−2)=−2⇒x=+4x + 3(-2) = -2 \Rightarrow x = +4x+3(−2)=−2⇒x=+4
56. The oxidizing agent is always the species that:
A) Loses electrons
B) Gains electrons
C) Gets oxidized
D) Donates protons
Answer: B
Explanation: Oxidizing agent gains electrons → gets reduced.
57. Reducing agent always:
A) Accepts electrons
B) Donates electrons
C) Gains oxygen
D) Gains protons
Answer: B
Explanation: Reducing agent donates electrons → gets oxidized.
58. In acidic medium, MnO₄⁻ reduces to:
A) Mn²⁺
B) MnO₂
C) Mn³⁺
D) Mn⁴⁺
Answer: A
Explanation: Mn⁷⁺ in permanganate is reduced to Mn²⁺ in acidic medium.
59. In neutral medium, MnO₄⁻ reduces to:
A) Mn²⁺
B) MnO₂
C) Mn³⁺
D) MnO₄²⁻
Answer: B
Explanation: In neutral medium, MnO₄⁻ → MnO₂.
60. In basic medium, MnO₄⁻ reduces to:
A) MnO₄²⁻
B) Mn²⁺
C) MnO₂
D) Mn³⁺
Answer: A
Explanation: Mn⁷⁺ → Mn⁶⁺ in basic medium (MnO₄²⁻).
61. Oxidation number of N in NO₂⁻ is:
A) +2
B) +3
C) +4
D) +5
Answer: B
Explanation: x+2(−2)=−1⇒x=+3x + 2(-2) = -1 \Rightarrow x = +3x+2(−2)=−1⇒x=+3
62. Oxidation number of N in NO₃⁻ is:
A) +2
B) +3
C) +5
D) +4
Answer: C
Explanation: x+3(−2)=−1⇒x=+5x + 3(-2) = -1 \Rightarrow x = +5x+3(−2)=−1⇒x=+5
63. Which of the following is an example of oxidation by loss of hydrogen?
A) CH₄ → CH₃OH
B) H₂S → S
C) H₂ → 2H⁺
D) NH₃ → N₂
Answer: B
Explanation: Loss of H indicates oxidation.
64. Which is an example of reduction by gain of hydrogen?
A) N₂ → NH₃
B) H₂S → S
C) Fe²⁺ → Fe³⁺
D) Cl₂ → 2Cl⁻
Answer: A
Explanation: N₂ gains hydrogen forming NH₃ (reduction).
65. Oxidation number of P in P₂O₅ is:
A) +3
B) +4
C) +5
D) +2
Answer: C
Explanation: 2x+5(−2)=0⇒x=+52x + 5(-2) = 0 \Rightarrow x = +52x+5(−2)=0⇒x=+5
66. Oxidation number of Cr in Cr₂O₃ is:
A) +2
B) +3
C) +6
D) +4
Answer: B
Explanation: 2x+3(−2)=0⇒x=+32x + 3(-2) = 0 \Rightarrow x = +32x+3(−2)=0⇒x=+3
67. Oxidation number of Mn in Mn₂O₇ is:
A) +4
B) +6
C) +7
D) +3
Answer: C
Explanation: 2x+7(−2)=0⇒x=+72x + 7(-2) = 0 \Rightarrow x = +72x+7(−2)=0⇒x=+7
68. Oxidation number of Cl in Cl₂O₇ is:
A) +5
B) +7
C) +6
D) +4
Answer: B
Explanation: 2x+7(−2)=0⇒x=+72x + 7(-2) = 0 \Rightarrow x = +72x+7(−2)=0⇒x=+7
69. Which is not a redox reaction?
A) NaOH + HCl → NaCl + H₂O
B) Zn + H₂SO₄ → ZnSO₄ + H₂
C) Fe + CuSO₄ → FeSO₄ + Cu
D) 2H₂ + O₂ → 2H₂O
Answer: A
Explanation: Neutralization reaction, no electron transfer.
70. Oxidation number of carbon in HCOOH is:
A) +1
B) +2
C) 0
D) +3
Answer: +2
Explanation: +1+x+2(−2)+(+1)=0⇒x=+2+1 + x + 2(-2) + (+1) = 0 \Rightarrow x = +2+1+x+2(−2)+(+1)=0⇒x=+2
71. Oxidation number of chlorine in ClO₃⁻ is:
A) +3
B) +5
C) +7
D) +1
Answer: B
Explanation: x+3(−2)=−1⇒x=+5x + 3(-2) = -1 \Rightarrow x = +5x+3(−2)=−1⇒x=+5
72. Oxidation number of S in H₂SO₃ is:
A) +4
B) +6
C) +2
D) +3
Answer: A
Explanation: 2(+1)+x+3(−2)=0⇒x=+42(+1) + x + 3(-2) = 0 \Rightarrow x = +42(+1)+x+3(−2)=0⇒x=+4
73. Oxidation number of N in N₂H₄ (hydrazine) is:
A) +1
B) -2
C) -1
D) 0
Answer: C
Explanation: 2x+4(+1)=0⇒x=−2 per molecule, −1 per N2x + 4(+1) = 0 \Rightarrow x = -2 \text{ per molecule, } -1 \text{ per N}2x+4(+1)=0⇒x=−2 per molecule, −1 per N
74. Oxidation number of C in CO is:
A) +1
B) +2
C) +4
D) -2
Answer: B
Explanation: x+(−2)=0⇒x=+2x + (-2) = 0 \Rightarrow x = +2x+(−2)=0⇒x=+2
75. Oxidation number of Fe in FeCl₃ is:
A) +2
B) +3
C) +1
D) 0
Answer: B
Explanation: x+3(−1)=0⇒x=+3x + 3(-1) = 0 \Rightarrow x = +3x+3(−1)=0⇒x=+3
76. Oxidation number of Cu in Cu₂O is:
A) +1
B) +2
C) 0
D) +3
Answer: A
Explanation: 2x+(−2)=0⇒x=+12x + (-2) = 0 \Rightarrow x = +12x+(−2)=0⇒x=+1
77. Oxidation number of Cu in CuO is:
A) +1
B) +2
C) 0
D) +3
Answer: B
Explanation: x+(−2)=0⇒x=+2x + (-2) = 0 \Rightarrow x = +2x+(−2)=0⇒x=+2
78. The oxidizing agent in
2H₂O₂ → 2H₂O + O₂ is:
A) H₂O
B) H₂O₂
C) O₂
D) None
Answer: B
Explanation: H₂O₂ decomposes; it acts as both oxidizing and reducing agent.
79. In a redox reaction, the sum of oxidation numbers of all atoms in a neutral compound is:
A) +1
B) 0
C) -1
D) Depends on element
Answer: B
Explanation: For a neutral compound, total oxidation number = 0.
80. Oxidation number of N in NH₂OH is:
A) +1
B) -1
C) -3
D) 0
Answer: -1
Explanation: x+3(+1)+(−2)+(+1)=0⇒x=−1x + 3(+1) + (-2) + (+1) = 0 \Rightarrow x = -1x+3(+1)+(−2)+(+1)=0⇒x=−1
81. Which of the following involves no change in oxidation number?
A) 2H₂ + O₂ → 2H₂O
B) BaCl₂ + H₂SO₄ → BaSO₄ + 2HCl
C) Zn + H₂SO₄ → ZnSO₄ + H₂
D) Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag
Answer: B
Explanation: Double displacement, no redox change.
82. Oxidation number of S in Na₂S₂O₃ (thiosulfate) is:
A) +2
B) +2 and +6
C) +2 average
D) +3
Answer: C
Explanation: Average oxidation state of S = +2; actual: +2 and +6.
83. Oxidation number of Cl in KClO is:
A) +1
B) +3
C) +5
D) +7
Answer: A
Explanation: +1+x+(−2)=0⇒x=+1+1 + x + (-2) = 0 \Rightarrow x = +1+1+x+(−2)=0⇒x=+1
84. Oxidation number of Br in BrO₃⁻ is:
A) +1
B) +3
C) +5
D) +7
Answer: C
Explanation: x+3(−2)=−1⇒x=+5x + 3(-2) = -1 \Rightarrow x = +5x+3(−2)=−1⇒x=+5
85. Oxidation number of S in SF₆ is:
A) +4
B) +6
C) +2
D) 0
Answer: B
Explanation: x+6(−1)=0⇒x=+6x + 6(-1) = 0 \Rightarrow x = +6x+6(−1)=0⇒x=+6
86. Oxidation number of N in N₂O₃ is:
A) +1
B) +2
C) +3
D) +4
Answer: C
Explanation: 2x+3(−2)=0⇒x=+32x + 3(-2) = 0 \Rightarrow x = +32x+3(−2)=0⇒x=+3
87. Oxidation number of N in NO is:
A) +1
B) +2
C) +3
D) +4
Answer: B
Explanation: x+(−2)=0⇒x=+2x + (-2) = 0 \Rightarrow x = +2x+(−2)=0⇒x=+2
88. Oxidation number of N in N₂O₅ is:
A) +3
B) +4
C) +5
D) +2
Answer: C
Explanation: 2x+5(−2)=0⇒x=+52x + 5(-2) = 0 \Rightarrow x = +52x+5(−2)=0⇒x=+5
89. Oxidation number of Cr in CrO₄²⁻ is:
A) +3
B) +4
C) +6
D) +5
Answer: C
Explanation: x+4(−2)=−2⇒x=+6x + 4(-2) = -2 \Rightarrow x = +6x+4(−2)=−2⇒x=+6
90. Oxidation number of Cr in Cr₂O₇²⁻ is:
A) +4
B) +6
C) +3
D) +2
Answer: B
Explanation: 2x+7(−2)=−2⇒x=+62x + 7(-2) = -2 \Rightarrow x = +62x+7(−2)=−2⇒x=+6
91. Oxidation number of Cl in Cl₂O is:
A) +1
B) +2
C) +4
D) +3
Answer: +1
Explanation: 2x+(−2)=0⇒x=+12x + (-2) = 0 \Rightarrow x = +12x+(−2)=0⇒x=+1
92. Oxidation number of Cl in ClO₂⁻ is:
A) +1
B) +3
C) +5
D) +7
Answer: +3
Explanation: x+2(−2)=−1⇒x=+3x + 2(-2) = -1 \Rightarrow x = +3x+2(−2)=−1⇒x=+3
93. In the reaction
2Na + Cl₂ → 2NaCl,
which is oxidized?
A) Na
B) Cl₂
C) NaCl
D) None
Answer: A
Explanation: Na → Na⁺ + e⁻ (oxidation).
94. Which is reduced in the same reaction?
A) Na
B) Cl₂
C) NaCl
D) None
Answer: B
Explanation: Cl₂ + 2e⁻ → 2Cl⁻ (reduction).
95. Oxidation number of Mn in KMnO₄ changes from +7 to +2 in acidic medium. The number of electrons gained per Mn atom is:
A) 3
B) 5
C) 2
D) 4
Answer: B
Explanation: +7 → +2 = gain of 5 electrons.
96. In the redox reaction, oxidation and reduction occur:
A) Separately
B) Simultaneously
C) Independently
D) Not at all
Answer: B
Explanation: Oxidation and reduction always occur together.
97. The species that accepts electrons is called:
A) Oxidizing agent
B) Reducing agent
C) Catalyst
D) Base
Answer: A
Explanation: Accepting electrons = reduction = oxidizing agent.
98. The species that donates electrons is called:
A) Oxidizing agent
B) Reducing agent
C) Acid
D) Catalyst
Answer: B
Explanation: Donating electrons = oxidation = reducing agent.
99. In redox reactions, the total increase in oxidation number equals:
A) Total decrease in oxidation number
B) Zero
C) Sum of oxidation states
D) None
Answer: A
Explanation: Electrons lost = electrons gained.
100. Which of the following best defines a redox reaction?
A) Reaction involving acids and bases
B) Reaction involving exchange of ions
C) Reaction involving oxidation and reduction simultaneously
D) Reaction involving proton transfer
Answer: C
Explanation: Redox reaction = simultaneous oxidation and reduction due to electron transfer.