Word Equations for Neutralisation

Introduction

Once you know that acid + base → salt + water, the only real challenge in writing a neutralisation equation is naming the salt correctly. Fortunately, salt names follow a simple two-part rule: the first word comes from the base and the second word comes from the acid. Learn four acid endings and you can name hundreds of salts, predict products you have never seen, and even work out how to make a particular salt from its name alone.

Core explanation

Part one: the metal from the base. The first word of the salt name is the metal (or ammonium) from the base. Sodium hydroxide gives sodium salts; copper(II) oxide gives copper(II) salts; calcium carbonate gives calcium salts; ammonia gives ammonium salts. Note the spelling change: ammonia becomes ammonium .

Part two: the ending from the acid. The second word depends only on the acid:

Acid Salt ending Example salt --- --- --- Hydrochloric acid chloride sodium chloride Sulfuric acid sulfate magnesium sulfate Nitric acid nitrate potassium nitrate Ethanoic acid ethanoate sodium ethanoate Citric acid citrate calcium citrate

Three types of base, three patterns.

1. Metal hydroxide: acid + metal hydroxide → salt + water sulfuric acid + sodium hydroxide → sodium sulfate + water 2. Metal oxide: acid + metal oxide → salt + water hydrochloric acid + copper(II) oxide → copper(II) chloride + water 3. Metal carbonate: acid + metal carbonate → salt + water + carbon dioxide nitric acid + calcium carbonate → calcium nitrate + water + carbon dioxide

And for ammonia: acid + ammonia → ammonium salt, for example hydrochloric acid + ammonia → ammonium chloride.

Working backwards. To make a named salt, split the name. Zinc sulfate needs zinc from a base — such as zinc oxide or zinc carbonate — and sulfate from sulfuric acid. Potassium chloride needs potassium hydroxide and hydrochloric acid. This reasoning is how chemists plan the preparation of salts.

Useful checks. Every word equation should have the reactants on the left and products on the right, separated by an arrow, with "+" between substances. Salt names never include the word "acid" or "hydroxide", and the metal name never changes (except ammonia to ammonium). Water appears in every acid–base neutralisation, and carbon dioxide appears only when a carbonate is used.

Step-by-step reasoning

To write a word equation for a neutralisation:

1. Write the names of the acid and base on the left, joined by "+". 2. Identify the type of base: hydroxide, oxide, carbonate or ammonia. 3. Name the salt: metal from the base, ending from the acid. 4. Add water, and carbon dioxide too if the base is a carbonate. 5. Check that the salt name contains no leftover "acid" or "hydroxide".

Visual explanation

Imagine two jigsaw pieces. The left piece is taken from the base and shows the metal name, such as "magnesium". The right piece is taken from the acid and shows the ending, such as "nitrate". Clicking them together gives "magnesium nitrate". Swap either piece and a different salt appears.

Real-world analogy

Naming a salt is like naming a person with a first name and a family name. The first name comes from the base and the family name comes from the acid. All "chlorides" belong to the hydrochloric acid family, just as siblings share a surname, while the first names tell them apart.

Real-world example

Bath salts often contain magnesium sulfate, known as Epsom salts. The name tells a chemist it could be made from sulfuric acid and a magnesium base such as magnesium oxide. Calcium citrate, used in some calcium supplements, similarly comes from citric acid and a calcium base.

Why?

Why does the ending come from the acid? When an acid dissolves, it releases H⁺ and leaves a negative ion — chloride from hydrochloric acid, sulfate from sulfuric acid, nitrate from nitric acid. That negative ion ends up in the salt, so it gives the salt its family name.

Common misconception

"Sulfuric acid makes sulfides." Sulfuric acid makes sulfates . Sulfides contain sulfur alone as the negative ion and come from a different source. Similarly, nitric acid makes nitrates, not nitrides.

Worked example

Question: Write the word equation for the reaction between hydrochloric acid and magnesium carbonate.

Reasoning: The base is a carbonate, so the products are a salt, water and carbon dioxide. The metal is magnesium and the acid gives the ending chloride.

Answer: hydrochloric acid + magnesium carbonate → magnesium chloride + water + carbon dioxide.

Quick check

1. Name the salt formed from nitric acid and sodium hydroxide. Answer: Sodium nitrate.

Exam focus

Learn the endings chloride, sulfate and nitrate for the three mineral acids. Examiners regularly ask you to complete word equations or to name the acid and base needed to make a given salt. Always remember carbon dioxide with carbonates.

Advanced insight

Once you can write word equations, the next step is symbol equations. For example, hydrochloric acid + sodium hydroxide → sodium chloride + water becomes HCl + NaOH → NaCl + H₂O. With sulfuric acid, two hydroxide units are needed for each acid molecule: H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O, which you will learn to balance later.

Summary

Salt names have two parts: the metal (or ammonium) from the base and the ending from the acid — chloride, sulfate, nitrate or ethanoate. Acids with hydroxides or oxides give salt + water; acids with carbonates give salt + water + carbon dioxide; acids with ammonia give ammonium salts. Splitting a salt's name shows which acid and base could make it.

Practice questions

1. Complete: sulfuric acid + potassium hydroxide → + water. Answer: Potassium sulfate. 2. Write the word equation for nitric acid reacting with copper(II) oxide. Answer: nitric acid + copper(II) oxide → copper(II) nitrate + water. 3. Name an acid and a base that could be used to make zinc chloride. Answer: Hydrochloric acid and zinc oxide (zinc carbonate or zinc hydroxide are also acceptable). 4. Write the word equation for sulfuric acid reacting with calcium carbonate. Answer: sulfuric acid + calcium carbonate → calcium sulfate + water + carbon dioxide. 5. What salt is formed when nitric acid reacts with ammonia? Answer: Ammonium nitrate.