1. Oxidation is defined as:
A) Gain of hydrogen
B) Loss of oxygen
C) Loss of electrons
D) Gain of neutrons
Answer: C) Loss of electrons
2. Reduction is the process of:
A) Loss of electrons
B) Gain of electrons
C) Gain of oxygen
D) Loss of hydrogen
Answer: B) Gain of electrons
3. In the reaction Zn + CuSO₄ → ZnSO₄ + Cu, zinc is:
A) Reduced
B) Oxidized
C) Neutralized
D) Precipitated
Answer: B) Oxidized
4. The oxidation number of oxygen in most compounds is:
A) 0
B) –1
C) –2
D) +2
Answer: C) –2
5. The oxidation number of hydrogen in most compounds is:
A) +1
B) –1
C) 0
D) +2
Answer: A) +1
6. Which of the following is an oxidizing agent?
A) Substance that loses electrons
B) Substance that gains electrons
C) Substance that loses protons
D) Substance that gains neutrons
Answer: B) Substance that gains electrons
7. Which of the following is a reducing agent?
A) Gains electrons
B) Loses electrons
C) Gains oxygen
D) Gains hydrogen
Answer: B) Loses electrons
8. In the reaction 2Mg + O₂ → 2MgO, magnesium undergoes:
A) Reduction
B) Oxidation
C) Hydrolysis
D) Neutralization
Answer: B) Oxidation
9. In a redox reaction, oxidation and reduction:
A) Occur separately
B) Never occur together
C) Occur simultaneously
D) Do not involve electrons
Answer: C) Occur simultaneously
10. Rusting of iron is an example of:
A) Reduction
B) Oxidation
C) Decomposition
D) Sublimation
Answer: B) Oxidation
11. The oxidation number of an element in its free state is:
A) +1
B) –1
C) 0
D) +2
Answer: C) 0
12. Which process involves gain of oxygen?
A) Reduction
B) Oxidation
C) Sublimation
D) Distillation
Answer: B) Oxidation
13. Which process involves loss of oxygen?
A) Oxidation
B) Combustion
C) Reduction
D) Evaporation
Answer: C) Reduction
14. In electrolysis, reduction occurs at the:
A) Anode
B) Cathode
C) Salt bridge
D) Electrolyte
Answer: B) Cathode
15. In electrolysis, oxidation occurs at the:
A) Cathode
B) Anode
C) Electrolyte
D) Container
Answer: B) Anode
16. The oxidation number of chlorine in NaCl is:
A) +1
B) –1
C) 0
D) +2
Answer: B) –1
17. Which of the following is reduced in the reaction CuO + H₂ → Cu + H₂O?
A) H₂
B) CuO
C) Cu
D) H₂O
Answer: B) CuO
18. The substance that is oxidized acts as a:
A) Oxidizing agent
B) Reducing agent
C) Catalyst
D) Precipitate
Answer: B) Reducing agent
19. The oxidation number of sulfur in H₂SO₄ is:
A) +4
B) +6
C) –2
D) 0
Answer: B) +6
20. Addition of hydrogen to a substance is called:
A) Oxidation
B) Reduction
C) Ionization
D) Dissociation
Answer: B) Reduction
21. Which reaction is a redox reaction?
A) HCl + NaOH → NaCl + H₂O
B) AgNO₃ + NaCl → AgCl + NaNO₃
C) 2KClO₃ → 2KCl + 3O₂
D) CaCO₃ → CaO + CO₂
Answer: C) 2KClO₃ → 2KCl + 3O₂
22. The oxidation number of carbon in CO₂ is:
A) +2
B) +4
C) –4
D) 0
Answer: B) +4
23. A decrease in oxidation number indicates:
A) Oxidation
B) Reduction
C) Combustion
D) Sublimation
Answer: B) Reduction
24. Which of the following involves both oxidation and reduction?
A) Double displacement reaction
B) Neutralization reaction
C) Redox reaction
D) Precipitation reaction
Answer: C) Redox reaction
25. The oxidation number of sodium in Na₂O is:
A) +1
B) +2
C) –1
D) 0
Answer: A) +1
26. In the reaction Fe₂O₃ + 3CO → 2Fe + 3CO₂, iron is:
A) Oxidized
B) Reduced
C) Neutralized
D) Hydrolyzed
Answer: B) Reduced
27. Which of the following is an example of oxidation?
A) Removal of oxygen
B) Gain of electrons
C) Loss of electrons
D) Addition of hydrogen
Answer: C) Loss of electrons
28. The oxidation number of nitrogen in NH₃ is:
A) –3
B) +3
C) 0
D) +5
Answer: A) –3
29. A substance that causes oxidation is called:
A) Reducing agent
B) Catalyst
C) Oxidizing agent
D) Base
Answer: C) Oxidizing agent
30. In the reaction Cl₂ + 2KI → 2KCl + I₂, chlorine is:
A) Reduced
B) Oxidized
C) Precipitated
D) Neutralized
Answer: A) Reduced