One similarity between all acids is that they contain hydrogen. When an acid dissolves in water, it provides hydrogen ions (H⁺), which are responsible for the acidic properties of the solution.
A base that dissolves in water is called an alkali. In an aqueous solution, alkalis provide hydroxide ions (OH⁻), which are responsible for the basic properties of the solution.
A neutralisation reaction is a chemical reaction between an acid and a base that forms a neutral solution of water and a salt. This reaction occurs because the H⁺ ions from the acid react with the OH⁻ ions from the alkali to form water. The ionic equation for this reaction is:
H⁺ (aq) + OH⁻ (aq) → H2O (l)
The solution formed by the neutralisation reaction is typically neutral if equal amounts of acid and base react, as pure water has a pH of 7. This means that the concentration of H⁺ ions and OH⁻ ions in the solution is equal
The salt produced in the reaction depends on the acid and the base used. For example, hydrochloric acid reacts with sodium hydroxide to produce sodium chloride and water, while sulfuric acid reacts with calcium hydroxide to produce calcium sulfate and water.
Metal oxides are compounds that contain a metal element and oxygen, and they are bases. When metal oxides dissolve in water, they produce basic solutions because they can react with hydrogen ions (H⁺) from acids to form a salt and water.
The general equation for the reaction between an acid and a metal oxide is:
Acid + Metal oxide → Salt + Water
Copper oxide + Sulfuric acid → Copper sulfate + Water
CuO (s) + H2SO4 (aq) → CuSO4 (aq) + H2O (l)
Metal hydroxides are compounds that contain a metal element, oxygen and a hydroxide group (OH⁻). They are also bases. When metal hydroxides dissolve in water, they produce basic solutions because they can react with hydrogen ions (H⁺) from acids to form water and a salt.
The reaction between an acid and a metal hydroxide is also called a neutralisation reaction. During this reaction, the metal hydroxide acts as a base, neutralising the acid to form a salt and water.
The general equation for the reaction between an acid and a metal hydroxide is:
Acid + Metal hydroxide → Salt + Water
Potassium hydroxide + Nitric acid → Potassium nitrate + Water
KOH (s) + HNO3 (aq) → KNO3 (aq) + H2O (l)
A carbonate is a compound that contains the carbonate ion (CO3²⁻). When an acid reacts with a carbonate, it produces a salt, water and carbon dioxide gas.
The general equation for the reaction between an acid and a carbonate is:
Acid + Carbonate → Salt + Carbon dioxide + Water
Calcium carbonate + Hydrochloric acid → Calcium chloride + Carbon dioxide + Water
CaCO3 (s) + 2HCl → CaCl2 (aq) + CO2 (g) + H2O (l)