Question

i) A black mineral (A) on treatment with dilute sodium cyanide of (B) and (C ).
ii) The solution of (B) on reaction with zinc gives precipitate of a metal (D).
iii) (D) is dissolved in dil. `HNO_(3)` and the resulting solution gives a white precipitate (E) with dil. HCl.
iv) (E) on fusion with sodium carbonate gives (D).
v) (E) dissolves in aqueous solution ammonia giveing a colourless solution (F).
The black mineral (A) is
A. `Ag_(2)S`
B. `PbS`
C. `CuS`
D. `HgS`

Answer 1

Correct Answer - A
`underset((A))(Ag_(2)S)+underset("dilute solution")(NaCN(aq.))overset("air")(rarr)underset((B))(Na[Ag(CN)_(2)])+underset((C ))(Na_(2)SO_(4))`
`2Na[Ag(CN)_(2)]+Zn rarr Na_(2)[Zn(CN)_(4)]+underset((D))(2Ag)`
`underset((D))(Ag)+"dil"HNO_(3)Ag^(+) +underset((E))(AgCl(s))`
`2AgCl(s)+underset((D))(Na_(2)CO_(3)2Ag)+CO_(2)+2NaCl+O_(2)^(-)`
`AgCl(s)+2NH_(3)rarr[Ag(NH_(3))_(2)]Cl`