Question

Bases insoluble in water are called alkalis.
A. True
B. False

Answer 1

Hint: Bases are the compounds which accept the electron pair from a solution. They can be soluble or insoluble or slightly soluble in liquids, particularly water. Both soluble bases and insoluble bases have little differences in their properties and so it is important to know about them.


Complete step by step solution:
-Compounds formed can fall under 3 categories, acids, bases and salts. Acids are electron pair donors, bases are electron pair acceptors and salts are formed as a neutralization reaction of acids and bases.
-Acids are the compounds that donate ${{H}^{+}}$ion to become anion. Bases are compounds that accept the ${{H}^{+}}$ion and convert into cation. Salts are the compounds formed mainly by the reaction of acids and bases.
-Some examples of bases as strong bases are NaOH, KOH, LiOH, $Ca{{\left( OH \right)}_{2}}$ and bases as weak bases are ammonia, pyridine.
-Soluble bases are called alkalis. They have their $pH$ greater than 7. They are soapy and slippery. They are defined differently due to the change in the properties of a soluble base and a non-soluble base.
-Both bases and acids dissociate to form a conjugate acid and a conjugate base. The bases which are not soluble in water do not give the hydroxyl ions and so they are treated differently from soluble bases called alkalis.
-There are two main uses of alkalis. One is that they easily dissolve the dirt and the grease stains thus helping in cleaning of the clothes and so are used as soaps and detergents. Another use is that they neutralize the acids and give the products salt and water. So, they are used even as toothpaste to remove acids in the mouth produced by bacteria.
-Basicity of an alkali is the number of hydroxyl ions an alkali can produce when it is mixed with water. Eg. NaOH has basicity of 1 while $Ca{{\left( OH \right)}_{2}}$has basicity of 2.
Their reactions can be written as
\[\begin{align}
& NaOH\left( aq \right)\to N{{a}^{+}}+O{{H}^{-}} \\
& \text{Ca}{{\left( OH \right)}_{2}}\left( aq \right)\to C{{a}^{2+}}+2O{{H}^{-}} \\
\end{align}\]
-A strong alkali dissociates completely to give hydroxyl ions while a weak alkali dissociates partially to give the hydroxyl ions. Eg. Sodium hydroxide is a strong alkali whereas aqueous ammonia is a weak alkali.
- Bases soluble in water are called alkali. Thus, all alkalis are bases but the vice versa is not true.

Therefore the statement is false.


Note: Whether strong or weak alkali, they can dissociate in water to give the hydroxyl ions only in aqueous medium. If the alkali is in solid state, it cannot dissociate itself to give the hydroxyl ions. So, we need to take care of the state of alkalis.