This how it works covers Making Insoluble Salts by Precipitation 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 7 of 13 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
⚙️ Making Insoluble Salts by Precipitation
Example: Making lead iodide (PbI₂) — a bright yellow precipitate
Pb(NO₃)₂(aq) + 2KI(aq) → PbI₂(s) + 2KNO₃(aq)
Method:
- Mix solutions of lead nitrate and potassium iodide
- Yellow precipitate of lead iodide forms immediately
- Filter to collect the precipitate
- Wash with distilled water (to remove soluble impurities)
- Dry in a warm oven or between filter papers
Quick Check: State whether lead iodide is soluble or insoluble, and predict how you would make it in the lab.
Lead iodide (PbI₂) is insoluble. Make it by precipitation: mix lead nitrate solution (Pb(NO₃)₂(aq)) with potassium iodide solution (KI(aq)). The bright yellow lead iodide precipitate forms immediately. Filter the mixture to collect the precipitate, then wash with distilled water to remove soluble impurities, and dry it.
Practice questions for Making Salts
Which of the following is the correct method for making copper sulfate crystals from copper oxide and sulfuric acid?
Describe the steps involved in the required practical for preparing a pure, dry sample of copper sulfate crystals from copper oxide and dilute sulfuric acid.