Question

21.In the test for nitrogen, the sodium fusion extract is acidified with which of the following? * 1 point Dilute sulphuric acid Dilute hydrochloric acid Concentrated hydrochloric acid Concentrated sulphuric acid​

Answer 1

Explanation:

Sodium fusion extract is acidified with nitric acid and then treated with silver nitrate. However if nitrogen and sulphur both are present, then Lassaigne's extract is boiled to expel nitrogen and sulphur which would otherwise interfere in the test for halogens.

Answer 2

Answer:

DILUTE SULPHURIC ACID

Explanation:

In organic compounds, nitrogen, sulphur and halogens are covalently bonded. Their detection in 'Lassaigne's test' is possible if they are in the ionic form. This can be achieved by fusing the organic compound with sodium metal.

Chemistry for test for nitrogen:

Sodium fusion extract is boiled with ferrous sulphate and acidified with sulphuric acid. Sodium cyanide reacts with ferrous sulphate and forms sodium hexacyanoferrate(II).  On heating with sulphuric acid, some ferrous is oxidized to ferric hexacyanoferate(II) Fe4[Fe(CN)6] 3 which is prussian blue in colour.

The existence of nitrogen can be confirmed if we get a Prussian blue colour. The ferrous ions oxidation is conducted by the acids, which are helpful to form ferric ions. The presence of nitrogen can be confirmed when there is the availability of the ferriferous cyanide in that solution.