An aqueous solution of a substance gives a white precipitate on treatment with dil. HCl which dissolves on heating and when $H_{2}S$ is passed through the hot acidic solution, black precipitate is obtained. The substance is

Q. An aqueous solution of a substance gives a white precipitate on treatment with dil $HCl$, which dissolved on heating. On passing $H_{2}S$ in hot acidic solution a black precipitate is formed. The substance is:

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

Q. An aqueous solution of a substance gives a white precipitate on treatment with dil $HCl$, which dissolved on heating. On passing $H_{2}S$ in hot acidic solution a black precipitate is formed. The substance is:

Q. A white crystalline substance dissolves in water. On passing $H_{2}S$ in this solution, a black precipitate is obtained. The black precipitate dissolves completely in hot $HN{O}_3$. On adding few drops of concentrated $H_{2}S{O}_4$, a white precipitate is obtained which is soluble in ammonium acetate. The white precipitate is that of

Q. In qualitative analysis when $H_{2}S$ is passed through an aqueous solution of salt acidified with dil. HCl, a black precipitate is obtained. On boiling the precipitate with dil. $HN{O}_3$ it forms a solution of blue colour. Addition of excess of aqueous solution of ammonia to this solution gives._____.