Saved Bookmarks
| 1. |
Given reasons: (i) During the test of nitrogen in Lassaigne's filtrate, sometimes red colouration is obtained when ferric chloride is added. (ii) Why is sodium extract made acidic with acetic acid before the addition of lead acetate in the test of sulphur? (iii) In the test of nitrogen, freshly prepared solution of ferrous sulphate is always used. (iv) During the test for halogens, why is sodium extract first boiled with a few drops of conc. HNO_(3)? (v) Why the organic compound is fused with sodium metal during detection of nitrogen, sulphur, halogens, etc.? (vi) What is the role of copper sulphate and potassium sulphate in Kjeldahl's process for the estimation of nitrogen in an organic compound? (vii) Is Beilstein test a satisfactory test for detection of halogens? (viii) Why C CI_(4) will not give white precipitate of AgCI on heating with AgNO_(3)? |
|
Answer» (ii) Lead acetate is hydrolysed by `NaOH` present in sodium extract. It is neutralised FIRST with acetic acid before the addition of lead acetate. (iii) Ferrous sulphate gets hydrolysed if its solution is stored. (iv) As to decompose `NaCN` or `Na_(2)S` if present in the sodium extract. (v) As to CONVERT nitrogen, sulphur or halogens present in an organic compound into ionisable substances. (vi) Copper sulphateacts as a catalyst while potassium sulphate raises the boiling point of `H_(2)SO_(4)`. (vii) It is not always reliable. Substances such as urea, thiourea, pyridine, organic acids, etc., ALSO impart COLOUR to flame. (vii) Because `C CI_(4)` is a covalent compound and hence does not ionise to give `CI^(-)` ions which is the essential requirement for `AgNO_(3)` test. |
|