A samlpe of 0.5 of an organic compound was analysed using Kjeldahl' method. The ammonia evolved was absorbed in 50 ml of 0.5 M `H_(2)SO_(4)`. The unsused acid after neutralisation by ammonia consumed 80 ml of 0.5N NaOH. Then calculate percentage of nitrogen in organic compound

Options

A. 14
B. 28
C. 42
D. 56

Answer

B

Explanation

Volume of acid taken = 50 mL of 0.5 `M H_(2)SO_(4)`
Let the volume of the acid left unused = v mL of M/10 `H_(2)SO_(4)`
Applying molarity equation,
`n_(a)M_(a)V_(a)` (acid) `= n_(b)M_(b)V_(b)` (base), we have, `2 xx 0.5 xx v = 1 xx 0.5 xx 80` or v = 40 mL
`:.` Volume of the acid used = 50 -40
= 10 mL of 0.5 M `H_(2)SO_(4)`
Now `%N = (1.4 xx n_(a)M_(a)V_(a))/("wt. of substance taken")`
`= (1.4 xx 2 xx 0.5 xx 10)/(0.5) = 28`