An queous solution of a substance gives a white precipitate on treating with dilute hydrochloric acid which dissolves on heating. When hydrogen sulphide is passed through the hot solution, a black precipitate is obtained. The substance is :

An queous solution of a substance gives a white precipitate on treatin

1.	An queous solution of a substance gives a white precipitate on treating with dilute hydrochloric acid which dissolves on heating. When hydrogen sulphide is passed through the hot solution, a black precipitate is obtained. The substance is :
Answer» `Hg^(2+)` salt `Cr^(3+)` salt `Ag^(+)` salt `Pb^(2+)` salt Solution :`Hg^(2+)` salt GIVES white precipitate with dilute HCl. `HgO + 2HCl rarr UNDERSET(("White ppt"))(HgCl_(2)) + H_(2)O` `HgCl_(2) + H_(2)S rarr underset(("Black ppt"))(HgS) + 2HCl`