Question

An acid having basicity of one and having only one replaceable hydrogen ion per molecule of the acid is:
A.Carbonous acid
B.Nitric acid
C.Sulphuric acid
D.Hydrochloric acid

Answer 1

pH scale is used to measure acidity or basicity. Basicity of an acid is given by the number of hydrogen ions present in it. The number of hydrogen atoms attached to oxygen in an acid will give the number of replaceable hydrogen atoms.

Complete step by step answer:
Carbonous acid having the formula $C{H_2}{O_2}$ . Here 2 hydrogen atoms are present. So, basicity will be 2. It is a dibasic acid.
Nitric acid having the formula HNO3. Here only one replaceable hydrogen atom is present. So, it is said to be a monobasic acid.

Sulfuric acid having the molecular formula ${H_2}S{O_4}$ . Here we can see that 2 replaceable hydrogens are present. So, it is said to be a dibasic acid.
Hydrochloric acid having the molecular formula HCl. Here only one replaceable hydrogen is present. So, HCl is said to be a monobasic acid.

Hence, the correct answer is B and D. Nitric acid and Hydrochloric acid are the acids having only one replaceable hydrogen atom.

Note: ${H_2}S{O_4}$ is the most important oxo acid of Sulphur. It acts as a very strong acid. It has a very high negative $p{K_a}$ value of first dissociation. $HN{O_3}$ is also a strong acid. It decomposes upon strong heating to $N{O_2}$ , ${O_2}$ water. HCl is prepared by heating sodium chloride with con. Sulfuric acid.