A sample of 0.5 g of an organic compound was treated according to Kjeldahl's method. The ammonia evolved was absorbed in 50 mL of 0.5 M H_(2)SO_(4). The remaining acid after neutralisation by ammonia consumed 80 mL of 0.5 M NaOH. The percentage of nitrogen in the organic compound is

A sample of 0.5 g of an organic compound was treated according to Kjel

1.	A sample of 0.5 g of an organic compound was treated according to Kjeldahl's method. The ammonia evolved was absorbed in 50 mL of 0.5 M H_(2)SO_(4). The remaining acid after neutralisation by ammonia consumed 80 mL of 0.5 M NaOH. The percentage of nitrogen in the organic compound is
Answer» 14 28 42 56 Solution :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`