Acidity or Hydrolysis Reactions. Definition: A Lewis acid is an electron pair acceptor Definition:...
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Transcript of Acidity or Hydrolysis Reactions. Definition: A Lewis acid is an electron pair acceptor Definition:...
Acidity or Hydrolysis Reactions
Definition: A Lewis acid is an electron pair acceptor
Definition: A Lewis base is an electron pair donor
In a complex, ligands donate a lone pair of electrons to the central metal ion
The ligands act as Lewis bases
The central metal ion act as a Lewis acid
In aqueous solutions, metal aqua ions are formed
The metal ions form hexaaqua complexes such as [M(H2O)6]2+ and [M(H2O)6]3+
These complexes have a octahedral shape with a co-ordination number of 6
Copper, cobalt and iron(II) form hexaaqua complexes in aqueous solution
Anhydrous white copper(II) sulfate dissolves in water to produce blue hexaaquacopper(II)
CuSO4 + 6H2O → [Cu(H2O)6]2+ + SO42-
White solid
Blue
Blue anhydrous cobalt(II) chloride dissolves in water to produce pink hexaaquacobalt(II)
CoCl2 + 6H2O → [Co(H2O)6]2+ + 2Cl-
Blue solid
Pink
Pale green iron(II) sulfate dissolves in water to produce pale green hexaaquairon(II)
FeSO4 + 6H2O → [Fe(H2O)6]2+ + SO42-
Pale green solid
Pale green
Aluminium is not a transition metal Aluminium forms a Al3+ ion
Aluminium chloride dissolves in water to produce hexaaquaaluminium(III)
Hexaaquaaluminium(III) is colourless as it is not a transition metal and therefore it has no d to d transitions
AlCl3 + 6H2O → [Al(H2O)6]3+ + 3Cl-
Colourless
Chromium(III) compounds such as chromium chloride dissolve in water to produce ruby hexaaquachromium(III)
CrCl3 + 6H2O → [Cr(H2O)6]3+ + 3Cl-
Ruby
Iron(III) compounds such as iron(III) chloride dissolve in water to produce pale violet hexaaquairon(III)
FeCl3 + 6H2O → [Fe(H2O)6]3+ + 3Cl-
Pale violet
Summary of hexaaqua colours:
Oxidation State Complex Colour+2 [Cu(H2O)6]2+ Blue
+2 [Co(H2O)6]2+ Pink
+2 [Fe(H2O)6]2+ Pale green
+3 [Al(H2O)6]3+ Colourless
+3 [Cr(H2O)6]3+ Ruby
+3 [Fe(H2O)6]3+ Pale violet