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Color and Complex Ions

Hazards

Nickel, copper, cobalt and chromium salts are toxic. Do not ingest.

Materials

  • HP Spectrophotometer
  • cuvettes
  • splitter cable for monitor

Procedure

  1. Arrange to borrow one of the HP spectrophotometers from the Chem 161/Chem 317 lab.
  2. Attach a splitter cable to the monitor jack and connect the monitor to the Imager projector interface box.
  3. Turn on the spectrophotometer.
  4. Type in uv and hit return.
  5. Choose F1 for general scanning.
  6. Choose F2 and type in the wavelength range 420 to 820.
  7. Choose F5 to select the Overlay mode of presentation.
  8. Place a blank in the sample holder and choose F8 to scan the blank.
  9. Replace the blank with your sample and press F1 to scan.

The spectrophotometer shows the absorption spectra of each colored solution. Sample spectra are shown in the demo write-up book.

Sample solutions

To show nickel complexes

  • green: \( \ce{Ni(H20)62+_{(aq)} } \) 
  • blue: \( \ce{Ni(NH3)62+_{(aq)} } \) 
  • purple: \( \ce{Ni(en)32+_{(aq)} } \) 

To show copper sulfate vs copper ammine

  • pale blue: copper sulfate solution aq.
  • super blue: \( \ce{Cu(NH3)62+_{(aq)} } \) 

To show variously colored substances

  • green: \( \ce{Ni(H20)62+_{(aq)} } \) 
  • super blue: \( \ce{Cu(NH3)62+_{(aq)} } \) 
  • purple: crystal violet (aq)
  • pink: \( \ce{Co(H20)62+(aq) } \) 
  • orange: potassium dichromate. aq.

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