250411802-SKT1013-Experiment-4.pdf - Experiment 4...

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Experiment 4: Preparation of Potassium Tri(oxalate)aluminate(III)trihydrate Objective 1. Synthesis potassium tri(oxalate)aluminate(III) trihydrate Reagents Apparatus Potassium Hydroxide (KOH) Oxalic Acid Dehydrate (H 2 C 2 O 4 . 2H 2 O) Ethanol Acetone Distilled Water Beaker (250 Ml) Graduated Cylinder Hot Plate Glass Rod Buchner Funnel Filter Paper Watch Glass Aluminium Foil Introduction Aluminium, like many of the transition metals, forms octahedral complex ions. In this lab we will synthesize potassium tris(oxalato)aluminate(III), K 3 [Al(C 2 O 4 ) 3 ]•3H 2 O. First, let’s cover some background on aluminium. Like several other metals, aluminium is reactive enough to displace hydrogen from water. However, this does not take place because aluminium develops a layer of aluminium oxide that protects the metal surface. This oxide coating can be dissolved by acid, according to the equation shown below. Al 2 O 3 + 3HCl → 6Cl - + 2Al 3+ + 3H 2 O But, in this experiment the oxide coating is dissolved by excess hydroxide, forming the

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