Balancing chemical equations — KCSE Chemistry

KCSE Chemistry · 66 practice questions · 4 syllabus objectives

25 easy17 medium24 hard

What You'll Learn

Key learning outcomes for this topic, aligned to the KNEC KCSE syllabus.

Apply the law of conservation of mass to balance chemical equations by inspection

Balance ionic equations including half-equations for redox reactions

Verify that a given equation is balanced and correct any errors

Balancing chemical equations

Sample Questions

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1
easySHORT ANSWER4 marks

Identify the changes in oxidation states and balance the following equation: ___H₂O₂ + ___I⁻ → ___I₂ + ___H₂O (4 marks)

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Part (a) — 2 marks
Oxidation state of I changes from -1 to 0 (2 mks)
Part (b) — 2 marks
2H₂O₂ + 2I⁻ → I₂ + 2H₂O (2 mks)
2
easySHORT ANSWER4 marks

Identify and balance the half-equations for the following redox reaction: Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s) (4 marks)

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Part (a) — 2 marks
Zn → Zn²⁺ + 2e⁻ (2 mks)
Part (b) — 2 marks
Cu²⁺ + 2e⁻ → Cu (2 mks)
3
easySHORT ANSWER4 marks

Identify the correct coefficients to balance the following redox reaction: ___MnO₄⁻(aq) + ___Fe²⁺(aq) → ___Mn²⁺(aq) + ___Fe³⁺(aq) (4 marks)

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Part (a) — 4 marks
2 for MnO₄⁻ (1 mk)
5 for Fe²⁺ (1 mk)
2 for Mn²⁺ (1 mk)
5 for Fe³⁺ (1 mk)
4

State the coefficients required to balance the following reactions: (a) __NH₃ + __O₂ → __NO + __H₂O (b) __C + __H₂O → __CO + __H₂ (c) __Al + __O₂ → __Al₂O₃

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Why Practise Balancing chemical equations?

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