Question

In Lassaigne's test for the detection of halogens, the sodium fusion extract is first boiled with concentrated nitric acid. This is

• A. to remove silver halides
• B. to decompose $ N{{a}_{2}}S $ and $ NaCN, $ if present
• C. to dissolve $ A{{g}_{2}}S $
• D. to dissolve $ AgCN, $ if formed
• E. because $ A{{g}_{2}}S $ and $ AgCN $ are insoluble in nitric acid

Answer 1

Answer: (B)

To test halogens, it is necessary to remove sodium cyanide and sodium sulphide from the sodium extract, if N and S are present. This is done by boiling sodium extract with conc
$ HN{{O}_{3}} $ . $ NaCN+HN{{O}_{3}}\xrightarrow{{}}NaN{{O}_{3}}+HCN\uparrow $ $ N{{a}_{2}}S+2HN{{O}_{3}}\xrightarrow{{}}2NaN{{O}_{3}}+{{H}_{2}}S\uparrow $