Helpful
Up0
DownNot Helpful
::
For knowing the reason first we have to know what is the base?
The compound which on reaction with water librates hydroxyl ion (OH-). The pH of the base is always greater than 7.
Now there’s a Strong Base and a Weak Base.
Strong Base: A base that is completely dissociated into its constituent ion when dissolved in water is called a Strong base. It usually acts as a strong electrolyte.
Example: Sodium hydroxide on reaction with water liberates sodium ion and hydroxyl ion.
Weak Base: A base that is not completely dissociated into its constituent ion when dissolved in water is called a Weak base. It usually acts as a weak electrolyte.
Example: Ammonia on reaction with water forms ammonium ion.
Ammonia is a base but doesn’t contain hydroxyl ion because when ammonia reacts with water it forms ammonium ion which on further ionization gives ammonium ion and hydroxyl ion. As hydroxide ion is liberated on ionizing, it is considered as the base even though it doesn’t contain hydroxyl ion.