The mole concept — KCSE Chemistry

KCSE Chemistry · 64 practice questions · 4 syllabus objectives

38 easy7 medium19 hard

What You'll Learn

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

Define the mole and Avogadro's constant and use them to calculate number of particles

Calculate molar mass of elements and compounds from their formulae

Convert between mass, moles and number of particles using n = m/M and N = n × Nₐ

The mole concept

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easyCalculation2 marks

Calculate the number of moles in 40 g of sodium chloride (NaCl) (Mr = 100).

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Part (a) — 2 marks

Using n = m/M; n = 40/100 (1 mk)

n = varies mol (1 mk)

easyCalculation2 marks

Calculate the number of moles in 40 g of calcium carbonate (CaCO₃) (Mr = 58.5).

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Part (a) — 2 marks

Using n = m/M; n = 40/58.5 (1 mk)

n = varies mol (1 mk)

easyCalculation2 marks

Calculate the number of moles in 140 g of sulphuric acid (H₂SO₄) (Mr = 100).

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Part (a) — 2 marks

Using n = m/M; n = 140/100 (1 mk)

n = varies mol (1 mk)

Calculate the number of moles in 120 g of sulphuric acid (H₂SO₄) (Mr = 40).

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