Question

In Kjeldahl's method, ammonia from $5\mathrm{g}$ of good neutralizes $30{\mathrm{cm}}^3$ of $0.1\mathrm{N}$ acid. The percentage of nitrogen in the food is:

• A. $0.84$
• B. $8.4$
• C. $16.8$
• D. $1.68$

Answer 1

The correct option is A

$0.84$

Explanation for correct answer:-

Option (A) $0.84$

Step 1: Given Data

Given,

The normality $\mathrm{N}=0.1\mathrm{N}$

The volume of the acid $\mathrm{V}=30{\mathrm{cm}}^3$

Mass of the acid $\mathrm{m}=5\mathrm{g}$

Step 2: Calculate using the Kjeldahl method

The kjeldahl method is the process in which it transforms all the nitrogen present in a given weighed sample into ammonium sulfate $\left({\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4\right)$.

According to Kjeldahl's method,

Percentage of Nitrogen, $\%\mathrm{N}=\frac{1.4\times \mathrm{N}\times \mathrm{V}}{\mathrm{m}}$

Upon substituting the values we get,

$\%\mathrm{N}=\frac{1.4\times 0.1\times 30}{5}$

$=1.4\times 0.1\times 6$

$=0.84$

Hence, the correct answer is an option (A).