Oxidation and Reduction Quiz - CBSE Class 12 Chemistry
Free practice quiz: Oxidation and Reduction (CBSE Class 12 Chemistry). 12 multiple-choice questions with answers and explanations. Play online, no sign-up needed.
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Which of the following represents oxidation?
- Gain of electrons
- Loss of electrons
- Gain of hydrogen
- Gain of oxygen
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Answer: B. Loss of electrons
Oxidation is defined as the loss of electrons by an atom, ion, or molecule.
In the reaction Zn + CuSO₄ → ZnSO₄ + Cu, which species is oxidized?
- Zn
- Cu
- SO₄²⁻
- Cu²⁺
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Answer: A. Zn
Zn loses electrons and becomes Zn²⁺, thus undergoing oxidation.
Identify the oxidizing agent in the reaction 2Fe³⁺ + Sn²⁺ → 2Fe²⁺ + Sn⁴⁺
- Fe³⁺
- Sn²⁺
- Fe²⁺
- Sn⁴⁺
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Answer: A. Fe³⁺
Fe³⁺ accepts electrons from Sn²⁺, causing its own reduction and the oxidation of Sn²⁺. Thus, Fe³⁺ is the oxidizing agent.
Explain why the oxidation state of oxygen is usually -2, but it can be different in peroxides and superoxides.
- Due to electronegativity differences
- Due to the presence of lone pairs
- Due to the formation of covalent bonds
- Due to the presence of unpaired electrons
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Answer: A. Due to electronegativity differences
Oxygen is highly electronegative, usually attracting two electrons to achieve a stable octet. However, peroxides (O₂²⁻) and superoxides (O₂⁻) have different structures leading to different oxidation states.
Discuss the application of redox reactions in the extraction of metals from their ores. Explain with the example of iron extraction.
- Redox reactions are irrelevant
- Redox reactions are used in some cases
- Redox reactions are used in most cases
- Redox reactions are used in all cases
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Answer: D. Redox reactions are used in all cases
Extraction of metals involves reduction of metal ions in ores using a reducing agent. In the case of iron, reduction of iron(III) oxide with carbon monoxide in a blast furnace is a key step.