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1. Complete and balance the following as net ionic equations. Assume the Cr and

ID: 521702 • Letter: 1

Question

1. Complete and balance the following as net ionic equations. Assume the Cr and Fe complexes will react completely with Cl- (or SCN-) to form an octahedral complex while the Cu complex will react to form a tetrahedral complex. If there was no discernable change within the observation period, write "no discernable reaction."

a) [Cr(H2O)6]3+ + Cl- ---->

b) [Cu(H2O)6]2+  + Cl-  ---->

c) [Fe(C2O4)3]3- + SCN- ---->

2. assign the previous complexes as inert or labile

3. does c have a high spin or low spin electron configuration?

Explanation / Answer

a) [Cr(H2O)6]3+ + 2Cl- ---->[ Cr(H2O)4Cl2]+ + 2H2O [common complex formed,green colored solution]

[Cr(H2O)6]3+ + 3Cl- ----> CrCl3 + 6H2O[anhydrous chromium chloride is green colored]

b) [Cu(H2O)6]2+  + 4Cl-  ----> [CuCl4]2-+6H2O

pale blue to yellow colored solution

octahedral hexaaquacopper(II) complex changes to tetrahedral tetrachlorocopper(II) complex ion.

Cl-is larger ligand than H2O and is charged,so tetrahedral geometry preferred as less repulsion between ligands takes place.

c) [Fe(C2O4)3]3- + SCN- ----> "no discernable reaction." as C2O42-(oxalate ) ions are chelating ligands that forms extra stable complex ,that do not undergo ligand exchange

2)[Cr(H2O)6]3+ is labile ,exchanges ligands

[Cu(H2O)6]2+ is labile

[Fe(C2O4)3]3- is inert ,stable,no exchange of ligand or geometry takes place

3)Fe3+ in octahedral complexes is low spin ,d5,t2g5eg0,one unpaired electron