Before the tests for halogens the Lassaigne's extract is to be boiled with dil. `HNO_(3)` - why?

Why is Lassaigne'extract not prepared with tap water?

Which of the following compounds is not dissolved in dil. HNO_(3) ?

Why do diazonium salts not respond to Lassaigne's test ?

PH_(3) has lower boiling point than NH_(3) . Why?

The boiling point NH_(3) is higher than that of PH_(3) but lower than BiH_(3) - why ?

In qualitative analysis, a black precipitate is obtained when H_(2)S is passed through an acidified aqueous solution of a salt . A blue coloured solution is obtained on boiling the preciptate with dilute HNO_(3) . The substance obtained on addition of excess of ammonia solution to this blue solution is -

Sulphur disappears when boiled with an aqueous solution of Na_(2)SO_(3) - Why ?

The products ul(X) and ul(Y) which are formed in the following sequence of reactions are respectively Phenol overset("dil HNO"_(3))to ulX underset(2.(CH_(3)CO)_(2)O"(1 equiv.)")overset(1.Zn//HCl,Delta)to ulY

Explain why iron and aluminium do not dissolve in conc. HNO_(3)