Question

What do you understand by an alkali? Give two examples of weak alkalis.

Answer 1

Alkali:

• An alkali is chemical species that is formed when a basic hydroxide is dissolved in water.
• The pH of an alkali or the solution of a base ranges from $8-14$ at ${25}^{\mathrm{o}}\mathrm{C}$.

Alkali can be classified into two categories:

1. Strong Alkali:

• An alkali that dissociates almost completely in an aqueous solution is called strong alkali.
• A high concentration of hydroxyl ions $\left({\mathrm{OH}}^{-}\right)$ are produced.
• Examples of strong alkali are Sodium hydroxide $\left(\mathrm{NaOH}\right)$ and Potassium hydroxide $\left(\mathrm{KOH}\right)$.

2. Weak Alkali:

• An alkali that dissociates partially in an aqueous solution is called weak alkali.
• A low concentration of hydroxyl ions $\left({\mathrm{OH}}^{-}\right)$ are produced.
• Examples of weak alkali are Calcium hydroxide $\left({\mathrm{CaOH}}_2\right)$ and Ammonium hydroxide $\left({\mathrm{NH}}_4\mathrm{OH}\right)$.