An aqueous solution of salt (A) gives a white crystalline precipitate (B ) with NaCl solution. The filtrate gives a black precipitate (C ) when `H_(2)S` gas is passed into it. Compound (B) is precipitate (D) with NaI solution and cooling. The compound (A) does not give any gas with dil HCl but liberates a reddish brown gas on heating. Identify the compounds A,B,C and D. Write the chemical equations for varius reactions involved.

Explanation

A gives white precipitate (B) with NaCl which is soluble in hot water and the, (B) may be `PbCl_(2)`. So (A) contains `Pb^(2+)` ions (2) (A) liberates reddish brown gas on heating and thus, it should have `NO_(3)^(-)` ions, (3) So, (A) in `Pb(NO_(3))_(2)`.
`(i) Pb(NO_(3))_(2)+2NaCl rarr underset((B))(PbCl_(2))+2NaNO_(3)`
`(ii) PbCl_(2)+H_(2)S rarr underset((C) "black ppt.")(PbS+2HCl)`
(iii) `underset((B))(PbCl_(2))+2NaI rarr underset("yellow ppt. (D)")(PbI_(2))+2NaCl`
(iv) `Pb(NO_(3))_(2)rarr PbO+2NO_(2)+(1)/(2)O_(2)`