Question

${ 10cm }^{ 3 }$ of ${ 0.1N }$ monobasic acid requires ${ 15cm }^{ 3 }$ of sodium hydroxide solution whose normality is:
A) ${ 1.5N }$
B) ${ 0.15N }$
C) ${ 0.066N }$
D) ${ 0.66N }$

Answer 1

Hint: Basicity of an acid is defined as the number of replaceable hydrogen atoms in one molecule of the acid. So a monobasic acid is an acid that contains one replaceable ${ H }^{ + }$ ion. One molecule of a monobasic acid gives one ${ H }^{ + }$ ion on dissociation.
Normality is the number of grams equivalent of a solute per liter of the solution.

Complete answer:
It is given that,
Normality of acid = ${ 0.1N }$
The volume of acid = ${ 10cm }^{ 3 }$
The volume of sodium hydroxide = ${ 15cm }^{ 3 }$
We have to calculate the normality of the sodium hydroxide solution

By the law of equivalency,
${ N }_{ 1 }{ V }_{ 1 }{ =N }_{ 2 }{ V }_{ 2 }$
${ 0.1N\times 10cm }^{ 3 }{ =N\times 15cm }^{ 3 }$
N = ${ 0.1N\times 10cm }^{ 3 }{ \div 15cm }^{ 3 }$
N = ${ 0.066N }$
Hence, the normality of sodium hydroxide solution is ${ 0.066N }$.

The correct answer is option C.

Additional Information:
Normality = (equivalents of solute)/Liter of solution
Gram equivalent is based on the equivalent weight concept. It is the measure of the mass proportion of an element or ion in which it combines with the mass of other chemical quantities.
In volumetric analysis, we use the concept of equivalent. So, here one equivalent of a reactant reacts with only one equivalent of another reactant.

Note:
The possibility to make a mistake is that you may choose option D. But here the normality of a monobasic acid is ${ 0.1N }$ and volume is ${ 10 }$ so, it comes out to be ${ 0.066N }$, not ${ 0.66N }$.