Question

Between Lab Period 1 and Lab Period 2, design a separation scheme for all 4 cations. Use the results of your preliminary tests and the reasoning illustrated in the introduction and the Week 2 Worksheet. Be sure to include equations for all the reactions which occur at each step in the scheme. Record the scheme in the data section of the lab notebook. The scheme MUST be submitted at the start of Lab Period 2. It will be reviewed by the TA at the start of the lab period, before you begin testing your scheme. Ag+, Fe 3+ Cu2+, Ni2+

Answer 1

SEPARATION SCHEME FOR CATIONS

GIVEN CATIONS :
`Ag^(+) \ , Fe^(3+) , Cu^(2+), Ni^(2+)`

Step 1: Add
`6mol/dm^3` of
`HCl` to the mixture solution

Result : This would cause a precipitate of
`AgCl` to be formed

Reaction :
`Ag^(+) _((aq)) + Cl^(-) _((aq)) ---------> AgCl(ppt)`

Step 2 : Next is to remove the precipitate and add
`H_2S` to the remaining

solution in the presence of
`0.2 \ mol/dm^3` of HCl

Result : This would cause a precipitate of
`CuS` to be formed

Reaction :
`Cu^(2+)_((aq)) + S^(2-)_((aq)) ------> Cu_2S(ppt)`

Step 3: Next remove the precipitate then add
`6 \ mol/dm^3` of aqueous

`NH_3 (NH_3 \cdot H_2 O)` , process the solution in a centrifuge,when the

process is done then sort out the precipitate from the solution

Now this precipitate is
`Fe(OH)_3` and the remaining solution

contains
`(Ni (NH_3)_6)`

Next take out the precipitate to a different beaker and add HCl

to it this will dissolve it, then add a drop of
`NH_4SCN` this will

form a precipitate
`Fe(SCN)_(6)^(3-)` which will have the color of

blood indicating the presence of
`Fe^(3+)`

Reaction :
`F^(3+)_((aq)) + 30H^-_((aq)) --------->Fe(OH)_3_((aq))`

`Fe (OH)_((s)) _3 + 3H^(+)_(aq) -------> Fe^(3+)_(aq) + 3H_2O_((l))`

`Fe^(3+) + 6SCN^(-) -----> Fe(SCN)_6 ^(3-)`

Now the remaining mixture contains
`Ni^(2+)`

Step-by-step explanation: