Chapter Exam

Chapter-9 Redox Reactions — Online MCQ Test

Q: Which of the following best defines oxidation in terms of oxygen?

Answer: B. Gain of oxygen by a substance — Oxidation in terms of oxygen is defined as the gain of oxygen by a substance. For example, when carbon burns to form carbon dioxide, carbon is oxidized.

Q: What is reduction in terms of electrons?

Answer: B. Gain of electrons — Reduction is defined as the gain of electrons by a substance. When a substance gains electrons, its oxidation state decreases, hence the term 'reduction'.

Q: In the reaction: Zn + CuSO₄ → ZnSO₄ + Cu, identify the substance that is reduced.

Answer: C. Copper — Copper ions (Cu²⁺) in copper sulfate gain electrons and are converted to copper metal, so copper is reduced. Zinc loses electrons and is oxidized.

Q: In the reaction: 2KMnO₄ + 10FeSO₄ + 8H₂SO₄ → K₂SO₄ + 2MnSO₄ + 5Fe₂(SO₄)₃ + 8H₂O, which species acts as the oxidizing agent?

Answer: B. KMnO₄ — KMnO₄ contains manganese in the +7 oxidation state, which is reduced to +2 in MnSO₄. The oxidizing agent is the substance that causes oxidation by accepting electrons, which is KMnO₄.

Q: In the reaction: 3Cu + 8HNO₃(dilute) → 3Cu(NO₃)₂ + 2NO↑ + 4H₂O, how many electrons are transferred per copper atom?

Answer: B. 2 electrons — Each Cu atom goes from 0 to +2 oxidation state, losing 2 electrons. Three Cu atoms lose 6 electrons total, and 2 N atoms (in HNO₃) go from +5 to +2, each gaining 3 electrons (6 total). This confirms 2 electrons per Cu atom on average.

CHEMISTRY · Grade 10 · IGCSE cambridge

Practice Chapter-9 Redox Reactions with a free chapter-wise online MCQ test for IGCSE cambridge Grade 10 CHEMISTRY. This chapter covers: Oxidation and reduction in terms of oxygen and electrons and identifying redox in reactions.. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter-9 Redox Reactions — Important Questions & Answers (FAQ)

Frequently asked questions from IGCSE cambridge Grade 10 CHEMISTRY — Chapter-9 Redox Reactions, with answers and explanations. These are sample questions; the exam has its own separate question set.

Which of the following best defines oxidation in terms of oxygen?

A. Loss of oxygen from a substance
B. Gain of oxygen by a substance ✓
C. Transfer of electrons to oxygen
D. Formation of oxygen gas

Answer: B. Gain of oxygen by a substance
Oxidation in terms of oxygen is defined as the gain of oxygen by a substance. For example, when carbon burns to form carbon dioxide, carbon is oxidized.

What is reduction in terms of electrons?

A. Loss of electrons
B. Gain of electrons ✓
C. Transfer of protons
D. Decrease in atomic number

Answer: B. Gain of electrons
Reduction is defined as the gain of electrons by a substance. When a substance gains electrons, its oxidation state decreases, hence the term 'reduction'.

In the reaction: Zn + CuSO₄ → ZnSO₄ + Cu, identify the substance that is reduced.

A. Zinc
B. Copper sulfate
C. Copper ✓
D. Sulfate ions

Answer: C. Copper
Copper ions (Cu²⁺) in copper sulfate gain electrons and are converted to copper metal, so copper is reduced. Zinc loses electrons and is oxidized.

In the reaction: 2KMnO₄ + 10FeSO₄ + 8H₂SO₄ → K₂SO₄ + 2MnSO₄ + 5Fe₂(SO₄)₃ + 8H₂O, which species acts as the oxidizing agent?

A. FeSO₄
B. KMnO₄ ✓
C. H₂SO₄
D. Fe₂(SO₄)₃

Answer: B. KMnO₄
KMnO₄ contains manganese in the +7 oxidation state, which is reduced to +2 in MnSO₄. The oxidizing agent is the substance that causes oxidation by accepting electrons, which is KMnO₄.

In the reaction: 3Cu + 8HNO₃(dilute) → 3Cu(NO₃)₂ + 2NO↑ + 4H₂O, how many electrons are transferred per copper atom?

A. 1 electron
B. 2 electrons ✓
C. 3 electrons
D. 4 electrons

Answer: B. 2 electrons
Each Cu atom goes from 0 to +2 oxidation state, losing 2 electrons. Three Cu atoms lose 6 electrons total, and 2 N atoms (in HNO₃) go from +5 to +2, each gaining 3 electrons (6 total). This confirms 2 electrons per Cu atom on average.

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