Reactions of acids

Acids take part in reactions in which salts are produced. In these reactions, the salt is formed by replacing the hydrogen ions in the acids with metal ions or ammonium ions.

Reactions with metals

A salt and hydrogen are produced when acids react with metals.

In general:

acid + metal → salt + hydrogen

For example:

hydrochloric acid + magnesium → magnesium chloride + hydrogen

2HCl(aq) + Mg(s) → MgCl2(aq) + H2(g)

Question

Hydrogen is collected in a test tube during the reaction between magnesium and hydrochloric acid. Describe the laboratory test for hydrogen.

Put a lighted splint near the mouth of the test tube. Hydrogen ignites with a squeaky pop.

Reactions with metal oxides

A salt and water are produced when acids react with metal oxides. Metal oxides are bases, because they neutralise acids.

In general:

acid + metal oxide → salt + water

For example:

sulfuric acid + copper oxide → copper sulfate + water

H2SO4(aq) + CuO(s) → CuSO4(aq) + H2O(l)

Reactions with metal hydroxides

A salt and water are produced when acids react with metal hydroxides. Metal hydroxides are bases because they neutralise acids.

In general:

acid + metal hydroxide → salt + water

For example:

nitric acid + sodium hydroxide → sodium nitrate + water

HNO3(aq) + NaOH(s) → NaNO3(aq) + H2O(l)

Reactions with carbonates

A salt, water and carbon dioxide are produced when acids react with carbonates.

In general:

acid + carbonate → salt + water + carbon dioxide

For example:

hydrochloric acid + copper carbonate → copper chloride + water + carbon dioxide

2HCl(aq) + CuCO3(s) → CuCl2(aq) + H2O(l) + CO2(g)

Question

Carbon dioxide is given off during the reaction between copper carbonate and hydrochloric acid. Describe the laboratory test for carbon dioxide.

Bubble the gas through limewater. Carbon dioxide turns limewater milky or cloudy white.

curriculum-key-fact
Metal oxides and metal hydroxides both react with acids to produce salts and water.