Question

The basicity of acetic acid is the same as the basicity of:
A. $HN{O_3}$
B. ${H_2}S{O_4}$
C. ${H_3}P{O_4}$
D. ${H_2}C{O_3}$

Answer 1

Basicity is defined as the number of replaceable hydrogen ions in a base. So, in order to find out the acid which has the same basicity as acetic acid, we should find the acid which has the same number of hydrogen ions which are replaceable from it as acetic acid.

Complete answer:
Basicity of acetic acid:
Chemical formula of acetic acid is: $C{H_3}COOH$
Ionisation of acetic acid is followed as:
$C{H_3}COOH \to C{H_3}CO{O^ - } + {H^ + }$
As it is clearly seen, that on ionisation acetic acid gives one hydrogen ion which is replaceable.
So basicity of acetic acid is $1$ .
Now, we have to calculate the basicity of all the acids given in the option to determine the acid which has basicity as same as acetic acid.
Now, in the case of $HN{O_3}$ ,
Ionisation of nitric acid is followed as:
$HN{O_3} \to N{O_3}^ - + {H^ + }$
So, on ionization nitric acid gives one replaceable hydrogen ion.
So the basicity of nitric acid is $1$ .
Now, in the case of sulphuric acid,
Ionisation of sulphuric acid is followed as:
${H_2}S{O_4} \to S{O_4}^{2 - } + 2{H^ + }$
So, on ionization sulphuric acid gives two replaceable hydrogen ion.
So the basicity of sulphuric acid is $2$ .
Now, in the case of phosphoric acid,
Ionisation of phosphoric acid is followed as:
${H_2}P{O_4} \to P{O_4}^{2 - } + 2{H^ + }$
So, on ionization phosphoric acid gives two replaceable hydrogen ion.
So the basicity of phosphoric acid is $2$ .
Now, in the case of carbonic acid,
Carbonic acid partially dissociates into a cation and anion.
Hence, basicity of acetic acid is equal to the basicity of nitric acid that is $1$ .
So, option A is correct.

Note:
The basicity of a molecule is a measure of its ability to accept a proton to form a stable product. If the product is a cation, then anything that stabilizes the positive charge will increase the strength of the base. Acidity of a molecule is a measure of its ability to donate a proton to form a stable product. Acidity can also be calculated as the number of hydroxyl ions which are replaceable from an acid.