# Copper(II) sulfate solution reacts with excess zinc powder. The equation for the reaction is: CuSO₄ + Zn → ZnSO₄ + Cu. A student wants to obtain 3.2 g of copper from this reaction. Calculate the minimum mass of zinc that must be used. Show your working. (Relative atomic masses: Cu = 64, Zn = 65, S = 32, O = 16)

> Edexcel A-Level Chemistry (9CH0) — 5.1 Calculations using moles · Explain · 5 marks

## Mark scheme (5 marks)

1. Correct molar mass of copper stated or used: Mr(Cu) = 64 g/mol
2. Correct calculation of moles of copper: moles = 3.2 ÷ 64 = 0.05 mol
3. Use of 1:1 molar ratio from the equation to state that moles of zinc = moles of copper = 0.05 mol
4. Correct molar mass of zinc stated or used: Mr(Zn) = 65 g/mol
5. Correct final answer: mass of zinc = 0.05 × 65 = 3.25 g

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