Making salts from metals and metal compounds

A soluble salt can be prepared by reacting an acid with a suitable insoluble reactant including:

The insoluble reactant chosen depends upon the particular salt required.

As the reaction between metals and acids produces flammable hydrogen, chemists usually make salts by reacting a metal compound such as a metal carbonate with an acid.

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 \rightarrow salt + hydrogen

For example:

hydrochloric acid + magnesium \rightarrow magnesium chloride + hydrogen

2HCl(aq) + Mg(s) \rightarrow MgCl2(aq) + H2(g)


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 carbonates

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

acid + carbonate \rightarrow salt + water + carbon dioxide

For example:

hydrochloric acid + copper carbonate \rightarrow copper chloride + water + carbon dioxide

2HCl(aq) + CuCO3(s) \rightarrow CuCl2(aq) + H2O(g) + CO2(g)


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.