Question

0.35 g of an organic substance was Kjeldahlised and the ammonia obtained was passed into 100 ml of N/5 H₂SO₄. The excess acid required 154 ml of N/10 NaOH for neutralisation. Calculate the percentage of nitrogen in the compound

Answer 1

Volume of N/5 H₂SO₄ solution taken = 100 mL 

The volume of N/5 H₂SO₄ neutralised by N/10 

NaOH can be obtained as follows :

 

= 77 mL 

Therefore, 

Volume of N/5 H₂SO₄ used for 

neutralising ammonia = (100 - 77) mL 

 = 23 mL 

Then, 

Percentage of nitrogen in the sample 

= 1.4 x Normality volume of acid

Percentage of nitrogen in the sample 

= 1.4 x 1/5 x 23 / 0.23 = 18.4