i)An acid may be defined as a substance that turn litmus red.
(ii)A base may be defined as a substance that turn litmus blue.
Litmus is a lichen found mainly in West Africa. It changes its colour depending on whether the solution it is in, is basic/alkaline or acidic. It is thus able to identify/show whether another substance is an acid, base or neutral.
(iii)An indicator is a substance that shows whether another substance is a base/alkaline,acid or neutral.
Common naturally occurring acids include:
|Name of Acid||Occurence|
|1.Citric acid||Found in ripe citrus fruits like passion fruit/oranges/lemon|
|2.Tartaric acid||Found in grapes/baking powder/health salts|
|3.Lactic acid||Found in sour milk|
|4.Ethanoic acid||Found in vinegar|
|5.Methanoic acid||Present in ants, bees stings|
|6.Carbonic acid||Used in preservation of fizzy drinks like coke, Lemonade, Fanta|
|7.Butanoic acid||Present in cheese|
|8.Tannic acid||Present in tea|
Most commonly used acids found in a school laboratory are not naturally occurring. They are manufactured. They are called mineral acids. Common mineral acids include:
|Name of mineral acid||Common use|
|Hydrochloric acid (HCl)||Used to clean/pickling surface of metals Is found in the stomach of mammals/human beings|
|Sulphuric(VI) acid (H2SO4)||Used as acid in car battery, making battery, making fertilizers|
|Nitric(V)acid (HNO3)||Used in making fertilizers and explosives|
Mineral acids are manufactured to very high concentration. They are corrosive (causes painful wounds on contact with the skin) and attack/reacts with garments/clothes/metals.
In a school laboratory, they are mainly used when added a lot of water. This is called diluting. Diluting ensures the concentration of the acid is safely low.
Bases are opposite of acids. Most bases do not dissolve in water. Bases which dissolve in water are called alkalis.
Common alkalis include:
|Name of alkali||Common uses|
|Sodium hydroxide (NaOH)||Making soaps and detergents|
|Potassium hydroxide(KOH)||Making soaps and detergents|
|Ammonia solution(NH4OH)||Making fertilizers, softening hard water|
Common bases (which are not alkali) include:
|Name of base||Common name|
|Magnesium oxide/hydroxide||Anti acid to treat indigestion|
|Calcium oxide||Making cement and neutralizing soil acidity|