Bases

Pay your attention to the substances classified under bases in the table prepared during assignment. Milk of magnesia, toothpaste, soap and lime are examples for bases.

Many bases are encountered as solids. Ammonia is a gas showing basic properties. Aqueous solutions prepared by dissolving bases in water are used in laboratory experiments. Sodium hydroxide (NaOH), potassium hydroxide (KOH) and ammonia solution (NH4 OH) can be given as the bases frequently used in the laboratory.

What is a base?

A base is a chemical compound that increases the hydroxyl ion (OH- ) concentration of an aqueous solution. For instance, in aqueous solution, sodium hydroxide (NaOH) ionises as follows and contributes to raise the OH- ion concentration.

Strong bases

The bases that completely ionise in aqueous solution are called strong bases. Examples for some strong bases and how they ionise in aqueous solution are given below.

•  Sodium hydroxide

•  Potassium hydroxide

Weak bases

The bases which partially ionise in aqueous solution are known as weak bases.

Ex : Ammonia solution (NH4 OH)

Properties of bases

They have a slimy texture as in soap.

Bases react with acids to give salts and water.

Bases turn red litmus blue. This is a simple test used to identify bases. Of the bases, those that readily dissolve in water are called alkalis.

Ex ( Sodium hydroxide (NaOH),  Potassium hydroxide (KOH),  Ammonia solution (NH4 OH)

Uses of some bases

Sodium hydroxide  

• Production of soap, paper, artificial silk and paints 
• Used in the laboratory as a strong base 
• Refining petroleum products 

Magnesium hydroxide 

• Magnesium hydroxide suspension (milk of magnesia) is used as an antacid to relieve gastritis (acidity in stomach) 
• Purification of molasses in sugar industry