CSEC CHEMISTRY · SECTION A · LESSON A12

Reactions of Acids, Neutralisation and Preparing Salts

How acids react with metals, bases, carbonates and hydrogencarbonates, neutralisation and its uses, preparing soluble and insoluble salts, and the solubility rules of salts.

Principles of ChemistryA 7.4A 7.6A 7.7A 7.8A 7.9A 7.10≈ 55 min🎮 3 games
Before you start

By the end of this lesson you can…

1WatchExplainer video 2ReadKey notes & exam tips 3PractisePaper 1 style 4ApplyPaper 2 style
Step 1 · Watch

Explainer video

5 narrated scenes. Press play, listen and read along — the points appear as they are explained. Use ‹ Prev / Next › or the scene bar to jump to any scene.

LESSON A12 · EXPLAINER

Reactions of Acids, Neutralisation and Preparing Salts

Antacids, fire extinguishers and baking powder all depend on one reaction: an acid meeting a carbonate. The same chemistry helps us make crystals of copper sulfate or a precipitate of lead iodide.

Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.

Step 2 · Read

Key notes

Copy these into your notebook in your own words — that is how they stick.

Acid + metal

Salt + hydrogen.

Acid + base

Salt + water (neutralisation).

Acid + carbonate

Salt + water + carbon dioxide.

Neutralisation ionic equation

H⁺ + OH⁻ → H₂O.

Soluble salt

Acid + excess insoluble base/metal/carbonate, filter, crystallise.

Group I salts

Titration, then evaporate.

Insoluble salt

Precipitation: mix, filter, wash, dry.

Uses

Antacids, baking powder, fire extinguishers, treating acidic soil and stings.

EXAM TIPS & COMMON MISTAKES

  • Describe the insoluble-salt method fully: mix solutions, filter, WASH with distilled water, dry (CXC January 2026 report).
  • Name the excess reactant in the soluble-salt method and why it is used (to ensure all the acid reacts).
  • Write the test for each gas: H₂ squeaky pop; CO₂ turns limewater milky.
  • Use the solubility rules to choose reagents for a precipitation.
Play & practise

Games

3 quick games on this lesson. Earn XP and badges as you play — your best score for each game is saved. Games are for practice and do not change your exam readiness. More games in the Chemistry Arcade.

Step 3 · Practise

Paper 1 practice — multiple choice

8 items modelled on real CSEC Paper 1 questions. Choose one answer for each, then check. Aim for 80% or better. Work each item on paper first.

Syllabus A 7.4

1. Dilute sulfuric acid reacts with zinc to produce

Answer: B. Acid + metal → salt + hydrogen.
Syllabus A 7.4

2. Dilute hydrochloric acid reacts with calcium carbonate to give a gas that

Answer: C. The gas is carbon dioxide.
Syllabus A 7.4

3. The ionic equation for neutralisation is

Answer: D. Hydrogen ions react with hydroxide ions.
Syllabus A 7.6

4. Copper(II) sulfate crystals are prepared by adding excess copper(II) oxide to warm dilute sulfuric acid. The excess oxide is removed by

Answer: A. Copper oxide is insoluble.
Syllabus A 7.9

5. Which salt is insoluble in water?

Answer: B. Lead iodide is a yellow precipitate.
Syllabus A 7.7

6. Barium sulfate can be prepared by mixing solutions of

Answer: C. Both are soluble; the barium sulfate precipitates.
Syllabus A 7.6

7. Sodium chloride is best prepared by

Answer: B. A Group I base is soluble, so no excess solid can be filtered off.
Syllabus A 7.8

8. Baking powder produces carbon dioxide when mixed with

Answer: D. Sodium hydrogencarbonate reacts with an acid.
Step 4 · Apply

Paper 2 practice — structured questions

Write full answers, then reveal the mark scheme and tick the points you earned (15 marks in total). Show all your working — method marks count. Your answers are saved on this device.

Paper 2 style · Salt preparation

Question 1 [15 marks]

Lead(II) iodide is an insoluble salt. Copper(II) sulfate is a soluble salt.

(a) (a) Describe how to prepare a dry sample of lead(II) iodide from solutions of lead(II) nitrate and sodium iodide. [5]

MARK SCHEME — (a) (max 5)

(b) (b) Write the ionic equation for the formation of lead(II) iodide. [2]

MARK SCHEME — (b) (max 2)

(c) (c) Describe how to prepare crystals of copper(II) sulfate from copper(II) oxide and dilute sulfuric acid. [5]

MARK SCHEME — (c) (max 5)

(d) (d) Explain why the copper(II) oxide is added in excess. [1]

MARK SCHEME — (d) (max 1)

(e) (e) Name a use of Epsom salts (magnesium sulfate) and one use of neutralisation. [2]

MARK SCHEME — (e) (max 2)

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Sources

Where this topic appears in CSEC papers

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