Chapter 7: Redox Reactions — Online MCQ Test
CHEMISTRY · CLASS 11 FIRST PUC · Karnataka State Board
Practice Chapter 7: Redox Reactions with a free chapter-wise online MCQ test.
This chapter covers: Oxidation Reduction Oxidation number Reducing agent Oxidising agent Electron transfer Redox equation Balancing reactions Disproportionation.
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Chapter 7: Redox Reactions — Important Questions & Answers
Which of the following best defines oxidation in terms of electron transfer?
- A. Gain of electrons
- B. Loss of electrons
- C. Gain of protons
- D. Loss of neutrons
Answer: B. Loss of electrons
Oxidation is defined as the loss of electrons. In redox reactions, the species that loses electrons is oxidized.
Oxidation is defined as the loss of electrons. In redox reactions, the species that loses electrons is oxidized.
Which species acts as a reducing agent in a redox reaction?
- A. Species that gains electrons
- B. Species that loses electrons
- C. Species that is not changed
- D. Species that always has oxidation number zero
Answer: B. Species that loses electrons
A reducing agent donates electrons to another species and itself gets oxidized. Hence, it loses electrons.
A reducing agent donates electrons to another species and itself gets oxidized. Hence, it loses electrons.
In the reaction CuO + H2 → Cu + H2O, which species is oxidised?
- A. CuO
- B. Cu
- C. H2
- D. H2O
Answer: C. H2
Hydrogen changes from oxidation number 0 in H2 to +1 in H2O, so it is oxidized. CuO is reduced to Cu.
Hydrogen changes from oxidation number 0 in H2 to +1 in H2O, so it is oxidized. CuO is reduced to Cu.
Which of the following represents the correct oxidation number change in the reaction 2FeCl2 + Cl2 → 2FeCl3?
- A. Fe: +2 to +3; Cl: 0 to -1
- B. Fe: +3 to +2; Cl: -1 to 0
- C. Fe: 0 to +2; Cl: 0 to +1
- D. Fe: +2 to 0; Cl: -1 to 0
Answer: A. Fe: +2 to +3; Cl: 0 to -1
Iron is oxidized from +2 to +3, while chlorine is reduced from 0 in Cl2 to -1 in FeCl3. This is a redox reaction.
Iron is oxidized from +2 to +3, while chlorine is reduced from 0 in Cl2 to -1 in FeCl3. This is a redox reaction.
Which one of the following is the correct balanced equation for the reaction of iron(II) with dichromate ion in acidic medium?
- A. Cr2O7^2- + 6Fe2+ + 14H+ → 2Cr3+ + 6Fe3+ + 7H2O
- B. Cr2O7^2- + 3Fe2+ + 14H+ → 2Cr3+ + 3Fe3+ + 7H2O
- C. Cr2O7^2- + 6Fe3+ + 14H+ → 2Cr3+ + 6Fe2+ + 7H2O
- D. 2Cr2O7^2- + 6Fe2+ + 14H+ → 4Cr3+ + 6Fe3+ + 7H2O
Answer: A. Cr2O7^2- + 6Fe2+ + 14H+ → 2Cr3+ + 6Fe3+ + 7H2O
Dichromate ion is reduced to Cr3+, and each Fe2+ is oxidized to Fe3+. The correct stoichiometric balance in acidic medium is Cr2O7^2- + 6Fe2+ + 14H+ → 2Cr3+ + 6Fe3+ + 7H2O.
Dichromate ion is reduced to Cr3+, and each Fe2+ is oxidized to Fe3+. The correct stoichiometric balance in acidic medium is Cr2O7^2- + 6Fe2+ + 14H+ → 2Cr3+ + 6Fe3+ + 7H2O.