A white solid dissolves in hot water. The hot solution gives a yellow precipitate with KI that dissolves on heating and recrystallises as golden spangles on cooling, and a white precipitate with dilute $H X_{2} SO X_{4}$ . The cation is

Answer: B

Golden spangles of yellow

PbI X_{2}

and white

PbSO X_{4}

identify

Pb X^{2 +}

(the solid is

PbCl X_{2}

Ag X^{+}

gives yellow AgI but no precipitate with

H X_{2} SO X_{4}

, and AgCl does not dissolve in hot water.

Hg X_{2} X^{2 +}

gives a green precipitate with KI.

Sn X^{2 +}

gives no sulphate precipitate.