Reactions of Acids with Metals

When a metal reacts with an acid, the reaction produces a salt and hydrogen. The general equation for this reaction is:

Acid + Metal Salt + Hydrogen

One example of such a reaction is when hydrochloric acid reacts with magnesium.

Hydrochloric acid + magnesium magnesium chloride + hydrogen

The symbol equation for this reaction is:

2HCl + Mg MgCl2 + H2

This reaction produces the salt magnesium chloride and hydrogen gas.

Naming the Salt

In acid-metal reactions, hydrogen gas is produced. This means that the only difference is the salt. Let’s look at two more examples:

Nitric acid + Sodium Sodium nitrate + hydrogen

Sulphuric acid + Calcium Calcium sulphate + hydrogen

  • The salt produced is in red

The salt name depends on what acid and metal are used. The first part of the name comes from the metal used and the second part comes from the acid. For example in our earlier example:

Hydrochloric acid + magnesium magnesium chloride + hydrogen

  • As we used magnesium, the name of the salt starts with ‘magnesium’
  • Because we used hydrochloric acid, the name of the salt ends with ‘chloride’

Remember these salt endings:

AcidSalt Ending
Hydrochloric acidChloride
Sulphuric acidSulphate
Nitric acidNitrate

You’ll know the reaction has occurred when you observe fizzing, which is hydrogen gas being released in the form of rising bubbles within the acid.

More reactive metals will have a more vigorous reaction. This means that the reaction will take place quicker and more bubbles will be released. For example, magnesium is more reactive than iron, so it will have a more vigorous reaction.

Some unreactive metals, such as copper or gold, may not react with dilute acids at all.

Testing for Hydrogen Gas

Hydrogen gas is always produced in metal-acid reactions, and you can perform a test to confirm the presence of hydrogen gas.

When the metal and acid react:

1. Place a boiling tube over the reacting acid and metal to collect the hydrogen gas.

2. Insert a lighted splint into the boiling tube.

3. If hydrogen is present, you will hear a squeaky pop.

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