A substance X when heated with conc.\(H_{2}SO_{4}\) liberates a gas which turns starch paper blue. The substance "X" is?

Kl when heated with conc . H_2SO_4 , it forms

KMnO_(4) is heated with conc. H_(2)SO_(4) gives

A solution of a sodium salt gives yellow precipitate with both Pb^(2+) and Ag^(+) ions. Moreover, the acidified solution of sodium salt with KNO_(2) liberates a coloured gas which turns starch paper blue. The anion is :

Formic acid when heated with conc . H_2 SO_4 produces …….. .

A substance on treatment with dil. H_2SO_4 liberates a colourless gas which turns acidified dichromate solution green. The reaction indicates the presence of

A white solid imparts a violet colour to a Bunsen flame. On being heated with concentrated H_(2)SO_(4) , the solid gives violet vapours that turn starch paper blue. The salt may be :