Question

Propose a method of separating: Hg2^2+, Cu^2+, Cr^3+, and Co^2+

Answer 1

Hg2^2+, Cu^2+, Cr^3+, and Co^2+

Group 1 metals --> Hg2+2

add HCl so

Hg2+2 + 2Cl- --> Hg2Cl2(s) is formed

filter and leave solution

Cu^2+, Cr^3+, and Co^2+ are left

in acidic media, add H2S

Cu+2 + S-2 --> CuS(s) is formed

filter and leave solution with

Cr^3+, and Co^2+ are left

Add NH4SCN so Cobalt complex forms:

Co(NO3)2 + 4 NH4SCN  (NH4)2[Co(SCN)4] + 2 NH4NO3

Now; add plenty of NaOH, so

Cr+3 + 3OH- -> Cr(OH)3(s) precipitates, filer

then

(NH4)2[Co(SCN)4] + H+ --> NH4+ + Co+2 + SCN- forms again

add OH-

Co(OH)3(s) precipitates; filter