Question

The basicity of an acid is defined as:
A. The number of replaceable $O{{H}^{-}}$.
B. The number of ${{H}^{+}}$ ions that can be formed from the acid.
C. The power of the acid to form salts.
D. None of the above.

Answer 1

Hint: The acidity and basicity of an acid can be known by the extent of hydroxyl ions and hydronium ions it will produce in aqueous solution. To find the correct option, try to define basicity and acidity of an acid.

Complete answer:
According to Bronsted-Lowry definition, acidity is the extent to which a substance donates a proton or a hydrogen ion (simply represented by ${{H}^{+}}$. Substances with high acidic value will tend to donate a proton whereas, the substances with low acidity will rarely donate any protons i.e. they will try to accept protons. While, basicity according to him is the extent to which a substance will accept a proton or hydrogen ion.
But, according to Lewis definition acid is defined as the substances that accept electron pairs while bases are the substances that donate an electron pair.
So, basicity of an acid is defined as the number of hydrogen ions which can be produced from one molecule of the acids on complete dissociation while acidity of a base is the number of hydroxyl ions which can be produced from one molecule of the base on complete dissociation. For example, on dissociation of acetic acid, it will produce a hydrogen ion. The reaction is shown below:
$C{{H}_{3}}COOH\rightleftharpoons C{{H}_{3}}CO{{O}^{-}}+{{H}^{+}}$

Hence, the correct option is B.

Note: Possibly you may be confused with the term basicity means it will produce hydroxyl ions ($O{{H}^{-}}$) but it will produce hydrogen ions on dissociation. For an acid, if the basicity is more, then we can say the strength of acid will be more and vice-versa.