Acids, Bases and Salts

Acids and Bases

Acids are substances that produce hydrogen ions (H+) when dissolved in water. Common examples include hydrochloric acid (HCl), sulphuric acid (H2SO4), and nitric acid (HNO3).
Bases are substances that react with acids and neutralise them. They produce hydroxide ions (OH-) when dissolved in water. Common examples are metal oxides, hydroxides and alkalis such as sodium hydroxide (NaOH) and ammonia (NH3).
The pH scale measures how acidic or alkaline a solution is. A pH value less than 7 means the substance is acidic, greater than 7 means the substance is basic/alkaline, and 7 means the substance is neutral.
Indicators are substances that change colour when they are in acidic or alkaline solutions. Litmus, phenolphthalein, and methyl orange are common examples of indicators.
Neutralisation is the reaction between an acid and a base to form a salt and water. For example, hydrochloric acid reacts with sodium hydroxide to produce sodium chloride (a salt) and water.

A salt is a substance made when the hydrogen ions of an acid are replaced by metal ions or ammonium ions.
Salts can be made by the reaction of acids with metals, base or alkali.
Soluble salts can be made by reacting an acid with a suitable insoluble reactant (either a metal, metal oxide, hydroxide or carbonate). The mixture is filtered to remove unreacted solid and then the filtrate is evaporated to produce the salt.
The name of a salt is made up of two parts, the first part is the name of the metal in the base or alkali, and the second part comes from the acid.
- Salts of hydrochloric acid are chlorides.
- Salts of sulphuric acid are sulphates.
- Salts of nitric acid are nitrates.

Acids, bases and salts are essential in numerous chemical processes across industries including medical, agricultural, food, and cleaning industries.
They play crucial roles in our daily life, for instance, in digestion (stomach acid), soaps and detergents (bases), seasoning (table salt), and batteries (sulphuric acid and various salts).