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Preparation of Salts

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Preparation of Salts

Cambridge (CIE) IGCSE Chemistry

The Big Idea: The method used to prepare a salt depends on whether the salt and its reactants are soluble in water — soluble salts use different routes than insoluble salts, and each method is carefully chosen to get the pure product you need.

Quick Summary

Soluble Salts (Method A)

Excess solid reactant → filter → evaporate → crystallise. Use metal, insoluble base, or carbonate in excess.

Soluble Salts (Method B)

Titration of alkali + acid → evaporate → crystallise. For soluble bases like NaOH.

Insoluble Salts

Mix two soluble solutions → forms precipitate → filter → wash → dry. Extended tier only.

Hydration

Salts contain water of crystallisation. Heating removes it; adding water restores it.

What Is a Salt?

A salt is any compound formed when the hydrogen atom(s) in an acid are replaced by a metal or ammonium ion. This sounds abstract, but think of it this way: acids have H⁺ ions. When those get swapped out for something else — like Na⁺, Cu²⁺, or NH₄⁺ — you've made a salt.

Salt Formation Rule

Hydrogen in acid + Metal/Ammonium = Salt

How to Name a Salt

Salt names have two parts:

First part: comes from the metal, metal oxide, or metal carbonate (the base or reactant)
Second part: comes from the acid used

Quick Rule:
• Hydrochloric acid → chloride salts
• Sulfuric acid → sulfate salts
• Nitric acid → nitrate salts

Salt Naming Examples

Sodium hydroxide + hydrochloric acid → sodium chloride

Zinc oxide + sulfuric acid → zinc sulfate

Calcium carbonate + hydrochloric acid → calcium chloride

Where Do We Use Salts?

Fertilisers (e.g. ammonium nitrate)
Batteries
Cleaning products
Healthcare products and medicines
Fungicides and pesticides

Solubility Rules

Whether a salt is soluble (dissolves in water) or insoluble (doesn't dissolve) determines which method you'll use to prepare it. You must memorise this table.

Type of Salt	Soluble (✓)	Insoluble (✗)
Sodium, potassium, ammonium	ALL	None
Nitrates	ALL	None
Chlorides	Most	Silver, lead(II)
Sulfates	Most	Barium, calcium, lead(II)
Carbonates	Na, K, NH₄ only	Most others
Hydroxides	Na, K, NH₄ only (Ca slightly)	Most others

Memory Tip:

Quick Check

Method A: Preparing Soluble Salts with Excess Solid Reactant

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Also in the full note

Method B: Preparing Soluble Salts by Titration
Preparing Insoluble Salts — Precipitation Reaction
Hydrated & Anhydrous Salts
Key Terms — Memorise These
Concepts Checklist
Exam Tips & Common Mistakes
Put It All Together: Full Practice Problems
Method A1: Using Excess Metal

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Preparation of Salts

Preparation of Salts

Quick Summary

What Is a Salt?

How to Name a Salt

Salt Naming Examples

Where Do We Use Salts?

Solubility Rules

Quick Check

Method A: Preparing Soluble Salts with Excess Solid Reactant

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