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Homework 6: Isomers of Coordination Complexes

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Write the chemical equations to represent the following two observations:

  • When \(\ce{Na2CO3(s)}\) is added to \(\ce{CuSO4(aq)}\), a green insoluble precipitate forms. If \(\ce{NH3}\) is added to the mixture, the precipitate begins to dissolve.


Which of the following complex ions would have the largest overall formation constant, \(\mathrm{K_f}\). Why? \(\ce{[Ni(H2O)6]^2+}\), \(\ce{[Ni(NH3)6]^2+}\), \(\ce{[Ni(en)3]^2+}\), \(\ce{[Ni(NH3)4(en)]^2+}\).


  1. Sketch the geometric isomers of \(\ce{[Cu(en)(H2O)2ClF]}\).
  2. Sketch the geometric isomers of \(\ce{[Co(NH3)2Br2(NO2)2]-}\).


  1. How many unpaired electrons should be in the octahedral complex \(\ce{[Fe(CN)6]^2-}\)?
  2. How many unpaired electrons would you expect in the octahedral complex, \(\ce{[Ni(NO2)3(NH3)3]-}\)? Comparison with the tetrahedral complex \(\ce{[Mn(SCN)4]}\), which has more unpaired electrons?


  1. The complex ion, \(\ce{[Zn(Cl)4]^2-}\) is diamagnetic. Using crystal field theory, determine its most probable structure.
  2. Would you expect \(\ce{[Ni(CN)4]^2-}\) to be paramagnetic or diamagnetic? Using this information, can you verify whether the structure is tetrahedral, octahedral, or square planar? Explain.


  1. The tetrahedral \(\ce{[Cu(NH3)4]^2+}\) complex ion has a dark blue color and tetrahedral ­­­­­­­­­­­­­\(\ce{­­­­­­­­­­­­­[Cu(CN)4]^2-}\) is orange. Explain this difference.
  2. Of the subsequent two solids, one is blue and the other is green: \(\ce{­­­­­­­­­­­­­CuSO4 . 5H2O}\) and \(\ce{­­­­­­­­­­­­­NiCl2 . 6H2O}\). Explain.