Question

$21g$ of $HN{O}_3$ is added to $250mL$ of water. Then choose the correct option:

• A. $\text{Strength of the solution is}21g{L}^{-1}$
• B. $\text{Molarity=2.33 M}$
• C. $\text{Normality}=\text{Molarity}$
• D. $\text{Normality}=2.66N$

Answer 1

The correct option is C $\text{Normality}=\text{Molarity}$

$\text{Molecular Mass of}HN{O}_3=1+14+(16\times 3)=63gmo{l}^{-1}$

$\text{Moles of}HN{O}_3=\frac{\text{Mass of}HN{O}_3}{\text{Molecular Mass of}HN{O}_3}\text{Moles of}HN{O}_3=\frac{21}{63}=\frac{1}{3}mol$
Strength of a solution is the ratio of mass of solute to the volume of solution in litres
$\text{Strength}=\frac{21\times 1000}{250}g{L}^{-1}=84g{L}^{-1}$
$\text{Molarity}=\frac{\text{Moles of solute}}{\text{Volume of solution (L)}}=\frac{1\times 1000}{3\times 250}\text{Molarity=1.33 M}$
Since $n_f$ of $HN{O}_3=1$
and
$\text{Normality}=\text{Molarity}\times n_f$
Therefore,
$\text{Normality}=\text{Molarity}=1.33N$

Hence, the correct answer is option (c).