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Colors of Nickel Coordination Complexes

Materials

  • 1.5 liter Erlenmeyer Flask with Stir Bar and Rubber Stopper
  • Magnetic Stir Plate
  • DI Water
  • Gloves and Goggles
  • Premeasured solutions:

                                  40 mL Nickle Nitrate

                                  80 mL 5M Ammonium Hydroxide

                                  40 mL 25% Ethylene Diamine Solution

                                  50 mL 1% Dimethylglyoxime Solution

                                 400 mL 1M Potassium Cyanide

     

Procedure

  1. Place a 1500ml flask containing about 500ml distilled water and a stirring bar on a magnetic stirrer and adjust stirring rate.     

         

    Add solutions in sequence and listen for oohs and aahs from the audience.

  2. Add  1M Ni(NO3)2 , turns green.
  3. Add  5M NH3, turns blue.
  4. Add  25% ethylenediamene solution, turns purple.
  5. Add  1% dimethylglyoxime solution, turns red.
  6. Add  1M KCN, turns orange.
  7. Wait for applause

      

Reactions

Ni(H2O)62+ (aq) + 6NH3 (aq) -> Ni(NH3)62+ (aq) + 6H2O

                        K(eq) = 1.2 x 109

Ni(NH3)62+ (aq) + 2etdm(aq) -> Ni(etdm)32+ (aq) + 6NH3 (aq)

                 K(eq) = 1.1 x 109

Ni(etdm)32+ (aq) + 2dmg(aq) -> Ni(dmg)2 (aq) + 3etdm(aq) + 2H+ (aq)

                          K(eq) = 1.3 x 10-1

Ni(etdm)32+ (aq) + 2dmg(aq) -> Ni(dmg)2 (s) + 3etdm(aq) + 2H+ (aq)

                   K(eq) = 1.35 x 105

Ni(dmg)2 (s) + 4 CN- (aq) -> Ni(CN)4-2 (aq) + 2 dmg- (aq)

                   K(eq) = 6.3 x 107