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# Homework 6: Isomers of Coordination Complexes

There are select solutions to these problems here.

## Q6.1

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.

## Q6.2

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

## Q6.3

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

## Q6.4

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?

## Q6.5

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.

## Q6.6

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.