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Colors of Nickel Coordination Complexes

Procedure

  1. Place a 1500ml flask containing 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 40ml 1M Ni(NO3)2 , turns green.
  3. Add 80ml 5M NH3, turns blue.
  4. Add 40ml 25% ethylenediamene solution, turns purple.
  5. Add 50ml 1% dimethylglyoxime solution, turns red.
  6. Add 400ml 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

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Last Updated: 5/23/02