A student wants to prepare a pure, dry sample of copper(II) sulfate crystals from copper(II) oxide and dilute sulfuric acid. Which method should the student use?

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Question

A student wants to prepare a pure, dry sample of copper(II) sulfate crystals from copper(II) oxide and dilute sulfuric acid. Which method should the student use?

Accepted Answer

Add excess copper(II) oxide to the acid, filter, then heat the filtrate until crystals start to form and allow to cool — Award 1 mark for identifying the correct procedure of adding excess insoluble base, filtering, and crystallising. A is incorrect — evaporating to dryness would produce anhydrous powder, not crystals, and may cause decomposition. C is incorrect — evaporating all water produces anhydrous copper(II) sulfate, not hydrated crystals. D is incorrect — 'equal volumes' is not a valid method for ensuring complete reaction and excess solid cannot be measured by volume.

Answer

Mix equal volumes of copper(II) oxide and sulfuric acid, then filter the mixture

Answer

Add excess copper(II) oxide to the acid, filter, then evaporate the filtrate to dryness

Answer

Add copper(II) oxide until the reaction stops, then evaporate all the water

Answer

Add excess copper(II) oxide to the acid, filter, then heat the filtrate until crystals start to form and allow to cool

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