Required Practical: Preparing a Pure, Dry Sample of a Soluble Salt
Part of Making Salts — GCSE Chemistry
This required practical covers Required Practical: Preparing a Pure, Dry Sample of a Soluble Salt within Making Salts for GCSE Chemistry. Revise Making Salts in Chemical Changes for GCSE Chemistry with 20 exam-style questions and 20 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 5 of 13 in this topic. Revise both the method and the reason for each step, because practical questions often test understanding rather than pure recall.
Topic position
Section 5 of 13
Practice
20 questions
Recall
20 flashcards
🧪 Required Practical: Preparing a Pure, Dry Sample of a Soluble Salt
Example: Making copper sulfate from copper oxide and sulfuric acid
CuO + H₂SO₄ → CuSO₄ + H₂O
Black copper oxide + sulfuric acid → blue copper sulfate + water
Method:
- Heat dilute sulfuric acid in a beaker using a Bunsen burner (gently warm, don't boil)
- Add excess copper oxide a spatula at a time, stirring after each addition
- Continue adding until no more dissolves and some black powder remains (this ensures all acid is used up)
- Filter the mixture to remove excess copper oxide (the filtrate is copper sulfate solution)
- Pour filtrate into an evaporating basin
- Heat gently to evaporate about half the water (until crystals start to form at edges)
- Leave to cool and crystallise slowly (slow = bigger, better crystals)
- Filter to collect crystals and pat dry with filter paper
Why add EXCESS base?
To make sure ALL the acid reacts. Leftover acid would contaminate your salt. Excess base is easy to remove by filtering.