Question

A solution of $H_{3}P{O}_4$ has a strength of 4.9% w/v. Find the normality of the solution.

• A. 0.5 N
• B. 0.3 N
• C. 1.5 N
• D. 0.5 N

Answer 1

The correct option is C 1.5 N

4.9% w/v means 4.9 g of $H_{3}P{O}_4$ will be present in 100 mL of solution.
Number of moles = $\frac{\text{given mass}}{\text{molar mass}}=\frac{4.9}{98}=0.05$

Putting the value in molarity formula,
Molarity = $\frac{\text{number of moles}}{\text{total volume (mL)}}\times 1000$
$=\frac{0.05}{100}\times 1000=0.5$ M
Normality = molarity $\times$ n-factor
= 0.5 M $\times$ 3 = 1.5 N