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Reaction of metals with water

When a metal reacts with water, a metal hydroxide and hydrogen are formed.

Group 1

Sodium reacts rapidly with cold water. The word equation is:

sodium + water → sodium hydroxide + hydrogen

The balanced chemical equation is:

2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)

Group 2

The formulae of a group 1 metal hydroxide is different to a group 2 metal hydroxide. This affects the balancing of the chemical equations.

Calcium reacts more slowly with cold water. The word equation is:

calcium + water → calcium hydroxide + hydrogen

The balanced chemical equation is:

Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g)

Reaction of metals with dilute acids

When a metal reacts with a dilute acid, a salt and hydrogen are formed.

The more reactive the metal, the more rapid the reaction is. A metal below hydrogen in the reactivity series will not react with dilute acids.

For example, magnesium reacts rapidly with dilute hydrochloric acid:

magnesium + hydrochloric acid → magnesium chloride + hydrogen

Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)

The salt magnesium chloride is dissolved in the water, so it has the state symbol (aq) meaning aqueous.

Here are some common acids, their formula and ions: