Solubility Rules for Ionic Compounds — Acids, Bases and Salt Preparations | IGCSE Chemistry | Examo

Solubility Rules for Ionic Compounds — Acids, Bases and Salt Preparations | IGCSE Chemistry | Examo

Exam Frequency Analysis

Past paper frequency (2018 to 2024)

This topic accounts for approximately 8% of your exam marks.

stable

Low

Stable8%

Soluble and insoluble salt preparation methods are consistently tested with multi-step answers.

Why solubility matters

Knowing which salts dissolve in water and which do not decides which preparation method to use
A soluble salt is built up in solution first and then crystallised out by evaporation
An insoluble salt is dropped out of solution by precipitation — mixing two soluble salts whose ions exchange to form the wanted insoluble product

Solubility patterns to memorise

Type of salt	Soluble in water	Insoluble exceptions
Sodium, potassium and ammonium salts	All	—
Nitrates	All	—
Chlorides	Most	Silver chloride, lead(II) chloride
Sulfates	Most	Barium sulfate, calcium sulfate, lead(II) sulfate
Carbonates	Sodium, potassium and ammonium carbonates only	The rest are insoluble
Hydroxides	Sodium, potassium and ammonium hydroxides; calcium hydroxide is sparingly soluble (limewater)	Most other metal hydroxides

Calcium hydroxide solution is what you know as limewater, used as the test for carbon dioxide