Recommended resources
The freely available resources this lesson will direct you to.
Hello. This first module builds a compact set of reaction patterns that appear frequently in science tests: acids reacting with metals, metal carbonates, and metal hydroxides. The key is not to memorise dozens of separate equations. Instead, identify the type of substance reacting with the acid, then use the acid to name the salt.
By the end of this lesson, you should be able to complete word equations using hydrochloric acid, sulfuric acid, or nitric acid and include every product.
The three reaction patterns
Start with the substance added to the acid. There are only three patterns to recognise in this lesson.
1. Acid and a reactive metal
A reactive metal displaces hydrogen from an acid. The products are a salt and hydrogen.
For example:
This reaction often produces bubbles. The gas is hydrogen, confirmed by a lighted splint making a characteristic squeaky pop.
Copper is below hydrogen in the reactivity series, so it does not react with dilute acids in this basic test pattern. A more reactive metal produces hydrogen more readily; the names of the products, however, follow the same rule.
2. Acid and a metal carbonate
A metal carbonate is identified by the word carbonate in its name, such as calcium carbonate or copper carbonate. The products are a salt, water, and carbon dioxide.
For example:
The carbon dioxide causes fizzing. It can be tested with limewater, which turns cloudy.
3. Acid and a metal hydroxide
A metal hydroxide is a base; if it dissolves in water, it is also called an alkali. Its name includes hydroxide, such as sodium hydroxide or magnesium hydroxide. The products are a salt and water.
For example:
This is a neutralisation reaction. Unlike the first two patterns, you should not expect a gas.
GCSE Chemistry Revision "Three Reactions of Acids"
Watch “GCSE Chemistry Revision: Three Reactions of Acids” from Freesciencelessons to see the hydroxide and carbonate patterns explained with word-equation examples.
Watch neutralisation to see why acids with bases or alkalis make salt and water, and how the acid determines the salt ending. Then watch carbonate reactions for the extra products, water and carbon dioxide. Pause briefly after each displayed example and compare its products with the three patterns above.
Naming the salt correctly
Every salt name has two useful parts:
- The metal name comes from the metal, metal carbonate, or metal hydroxide.
- The ending comes from the acid.
| Acid used | Salt ending | Example salt |
|---|---|---|
| Hydrochloric acid | chloride | calcium chloride |
| Sulfuric acid | sulfate | zinc sulfate |
| Nitric acid | nitrate | sodium nitrate |
This is the central naming rule for this topic:
- Hydrochloric acid always makes a chloride.
- Sulfuric acid always makes a sulfate.
- Nitric acid always makes a nitrate.
For instance, when sulfuric acid reacts with zinc oxide, the zinc supplies the first part of the salt name and sulfuric acid supplies the ending: zinc sulfate. In this lesson, the reactant may be a metal, carbonate, or hydroxide, but the salt is named in the same way.
Keep any detail already provided in the reactant name. If the reactant is called iron(II) carbonate, the salt is iron(II) sulfate or iron(II) nitrate, not simply “iron sulfate” or “iron nitrate.”
Reactions with acids - Making salts - GCSE Chemistry (Single ... - BBC
Read the BBC Bitesize guide “Reactions with acids” to reinforce the three product patterns and the observations that distinguish the gases.
On the “Reactions with acids” page, begin with the subsection “Acids and reactive metals.” Read the metal reaction explanation, including the zinc example and hydrogen test. Then move to “Acids and metal hydroxides (alkalis)” and continue through “Acids and metal carbonates.” Read the hydroxide and carbonate sections. Focus particularly on which reaction produces no gas, hydrogen, or carbon dioxide.
A reliable method for completing any word equation
When an exam question gives you a partly completed word equation, work in this order.
- Find the acid. Decide whether it gives chloride, sulfate, or nitrate.
- Classify the other reactant. Look for a plain reactive metal, the word carbonate, or the word hydroxide.
- Choose the product pattern. This determines whether hydrogen, water, and carbon dioxide must appear.
- Build the salt name. Use the metal name first and the acid ending second.
- Check that no product is missing. Carbonate reactions are especially easy to underwrite: they make both water and carbon dioxide.
Here are three fully worked examples.
Example A: a metal
The reactants are magnesium and nitric acid.
- Magnesium is a reactive metal.
- A metal plus acid makes salt and hydrogen.
- Nitric acid makes a nitrate salt.
Example B: a carbonate
The reactants are nitric acid and calcium carbonate.
- The word carbonate identifies the reaction type.
- A carbonate plus acid makes salt, water, and carbon dioxide.
- Nitric acid gives nitrate.
- Calcium supplies the metal part of the salt name.
Example C: a hydroxide
The reactants are sulfuric acid and sodium hydroxide.
- The word hydroxide identifies a metal hydroxide.
- A hydroxide plus acid makes salt and water.
- Sulfuric acid gives sulfate.
- Sodium supplies the metal part of the salt name.
Avoiding common exam errors
The reaction patterns are short, but a single omitted word can lose a mark. Watch for these errors:
- Writing “hydrochloride” as the salt ending. The correct ending is chloride.
- Mixing up the gas products.
Metals with acids produce hydrogen.
Carbonates with acids produce carbon dioxide. - Leaving out water in a carbonate reaction. Carbonate reactions make three products: salt, water, and carbon dioxide.
- Adding hydrogen to a hydroxide reaction. Acid plus metal hydroxide produces only salt and water.
- Using the acid name as the salt name. Sulfuric acid does not make “sulfuric zinc”; it makes zinc sulfate.
A useful final check is to say the equation aloud. If you hear “carbonate,” you should expect the phrase “water and carbon dioxide” among the products. If you hear “hydroxide,” the products should end with “salt and water.”
Key takeaways
You now have the complete pattern set:
Remember the salt endings: hydrochloric acid makes chlorides, sulfuric acid makes sulfates, and nitric acid makes nitrates. Combine that ending with the metal name, then make sure the correct additional products are present.
The next lesson begins the electrical section of the course by examining why a lithium ion has a positive charge, using its numbers of protons and electrons.