Question

`Co^(2+) + KCN` (not in excess) `to` precipitate.
Select the correct statement(s) with respect to the precipitate.
A. It is yellow in colour
B. It is reddish-brown in colour
C. It dissolves in excess of the reagent forming a brown solution
D. It is obtained when brown solution (option C) is acidified with dilute `HCl` in the cold.

Answer 1

Correct Answer - B,C,D
`Co^(2+)+2CN^(-)toCo(CN)_(2)darr`(reddish-brown)
`Co(CN)_(2)darr +4CN^(-)("excess")to [Co(CN)_(6)]^(4-)` (brown solution)
`[Co(CN)_(6)]^(4-)+4H^(+)to Co(CN)_(2)darr +4HCN`