GCSE · Chemistry · AQA · Spec 8462

Neutralisation and salt production

Table salt is just one member of a huge family — and two quick questions let you name any of them.

Chemistry · Predicting products

Walk the reaction: what forms?

Pick what the acid is reacting with, then pick the acid. The end of the path shows everything that forms.

What the acid reacts with → Which acid

  • Two questions decide everything. First: what is the acid reacting with? That tells you whether carbon dioxide forms. Second: which acid is it? That gives the salt the second part of its name.

9 possible reactions.

On An acid is neutralised by…. 3 branches to choose from.

Look down any one branch: the first word of every salt is the same metal. Look across the branches: the same acid always gives the same family. Two choices, one full name.

Chemistry · Your turn to predict

New reactants, same two questions

Pick a reaction, then pick where it belongs. Commit before you read why.

Does this reaction give off carbon dioxide as well as a salt and water?

Still to sort

Salt + water (0)

Acid + alkali, or acid + base.

Where the line is: No carbonate among the reactants means no carbon, so no carbon dioxide.

Salt + water + carbon dioxide (0)

Acid + metal carbonate.

Where the line is: Only the carbonate brings the carbon that leaves as carbon dioxide.

6 of 6 still to sort.

None of these pairs was on the tree. Sort each one first by what forms, then switch and sort by salt family.

From a name to a formula

Problem

Zinc oxide reacts with nitric acid. Name the salt and work out its formula. (Zinc ions are Zn²⁺.)

Chemistry · Now you do it

Fill the gaps: name it, then build its formula

Potassium carbonate reacts with sulfuric acid. Name the salt and work out its formula. (Potassium ions are K⁺.)

  1. Potassium carbonate is a metal carbonate, so the products are a salt, water and carbon dioxide.
  2. missing step
Which line is step 2?

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Two questions name any salt: what did the acid meet, and which acid was it?

What you need to know

  • Acid + alkali (a soluble metal hydroxide, such as sodium hydroxide) → salt + water.
  • Acid + base (an insoluble metal hydroxide or a metal oxide, such as copper oxide) → salt + water.
  • Acid + metal carbonate → salt + water + carbon dioxide.
  • Hydrochloric acid makes chlorides (Cl⁻), nitric acid makes nitrates (NO₃⁻) and sulfuric acid makes sulfates (SO₄²⁻).
  • The positive ion in the alkali, base or carbonate gives the salt the first part of its name.

The big picture

When an acid is neutralised by an alkali or a base, a salt and water form; when it reacts with a metal carbonate, carbon dioxide forms as well. Every salt's name has two parts: the metal from the alkali, base or carbonate comes first, and the acid decides the second part — hydrochloric acid makes chlorides, nitric acid makes nitrates and sulfuric acid makes sulfates. To write a salt's formula, you choose how many of each ion you need so that the positive and negative charges cancel to zero.

Key points

1Two questions predict everything: what did the acid meet, and which acid was it?
2Of the three partners, only the carbonate contains carbon — so only the carbonate gives off carbon dioxide.
3Metal first, acid family second: copper oxide + sulfuric acid gives copper sulfate.
4'Salt' names a whole family of compounds; sodium chloride is just one member of it.
5Fix a formula by changing how many of each ion you use, never the ions themselves — and bracket a group ion such as NO₃⁻ when you need more than one.

Worked example

Problem

Calcium carbonate reacts with hydrochloric acid. Name all the products, and write the formula of the salt. (Calcium ions are Ca²⁺.)

⚠ Watch out

Naming the salt from the acid alone. 'A sulfate' isn't a full name — you need the metal too, as in copper sulfate or magnesium sulfate.

🧠

Memory hook

Metal first, acid last — and only a carbonate brings the gas.

✓

Check yourself

Cover the page. Lithium carbonate reacts with nitric acid: what are all three products, and what is the formula of the salt if lithium ions are Li⁺?

Flashcards

(8)
What forms when an acid reacts with an alkali or a base?
A salt and water.
Which extra product forms when an acid reacts with a metal carbonate — and where does it come from?
Carbon dioxide, as well as a salt and water. Its carbon comes from the carbonate.
Alkali or base: what is the difference in this topic?
An alkali is a soluble metal hydroxide (e.g. sodium hydroxide). A base here is an insoluble metal hydroxide or a metal oxide (e.g. copper oxide). Both give a salt and water with an acid.
Which family of salts does each acid make?
Hydrochloric acid → chlorides. Nitric acid → nitrates. Sulfuric acid → sulfates.
Where does the FIRST part of a salt's name come from?
The positive ion — the metal — in the alkali, base or carbonate.
Give the formula and charge of the chloride, nitrate and sulfate ions.
Chloride Cl⁻, nitrate NO₃⁻, sulfate SO₄²⁻ (the only one of the three with a 2− charge).
How do you decide how many of each ion go into a salt's formula?
Pick the numbers that make the total positive charge cancel the total negative charge, so the overall charge is zero.
When does a salt's formula need brackets?
When you need more than one of a group ion, such as nitrate or sulfate: the whole ion goes in brackets with the number outside.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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