Unit Overview
Acids, Bases and Salts
CIE IGCSE Chemistry· 5 min read 📊 8-10% of combined MCQ and structured question sections
1. Unit at a glance
You will start by exploring the defining chemical and physical properties of acids and bases, including their effects on indicators, reaction rates, and product formation when reacted with common laboratory reagents.
You will then move to classifying different oxide types, before learning to select and carry out appropriate salt preparation methods, depending on whether the target salt is soluble or insoluble in water.
Work through the following sub-topics in order to master this unit:
Characteristic Properties of Acids and Bases
Covers the pH scale, indicator colour changes, and common reaction pathways for strong/weak acids and alkalis.
★★⏱ 10 min
Oxides and Preparation of Salts
Explores oxide classification, solubility rules, and step-by-step methods to prepare pure dry salt samples in the lab.
★★★⏱ 12 min
2. Common Pitfalls
Wrong move:
Assuming all metals react with acids to produce salt and hydrogen
Why:
Metals below hydrogen in the reactivity series (e.g. copper, silver) do not react with dilute acids
Correct move:
Cross-reference the reactivity series before predicting acid-metal reaction outcomes
Wrong move:
Using the same preparation method for all salts
Why:
Soluble and insoluble salts require completely different synthetic pathways
Correct move:
First check salt solubility using standard rules to select the right preparation approach
Wrong move:
Classifying all metal oxides as basic
Why:
Some metal oxides (e.g. aluminium oxide, zinc oxide) are amphoteric, reacting with both acids and bases
Correct move:
Memorize common amphoteric oxides and test for reactivity with both acidic and alkaline reagents
3. Quick Reference Cheatsheet
Concept/Formula | Description | Relevant Subtopic |
|---|---|---|
pH Scale | Acids have pH <7, neutral solutions pH=7, bases/alkalis pH >7 | Characteristic Properties of Acids and Bases |
Neutralization General Reaction | Acid + Base → Salt + Water | Characteristic Properties of Acids and Bases |
Acid + Carbonate General Reaction | Acid + Carbonate → Salt + Water + Carbon Dioxide | Characteristic Properties of Acids and Bases |
Oxide Classification | Acidic (non-metal, reacts with bases), Basic (metal, reacts with acids), Amphoteric (reacts with both), Neutral (reacts with neither) | Oxides and Preparation of Salts |
Insoluble Salt Preparation | Precipitation: mix two soluble salt solutions with desired ions, filter, wash, dry | Oxides and Preparation of Salts |
Soluble Salt Preparation | Excess solid (metal/base/carbonate) + acid, filter, crystallize product | Oxides and Preparation of Salts |
What's Next
You are ready to start your first sub-topic on the characteristic properties of acids and bases, where you will learn to identify acids and bases using indicators and predict their reaction products. Once you complete both sub-topics in this unit, you will move on to the next unit covering chemical energetics.