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

Answer:

                    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 $Ni^{2+}$

     

       

Explanation: