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EXPERIMENT 4 PREPARATION OF POTASSIUM TRIS (OXALATO)-ALUMINATE (III) TRIHYDRATE OBJECTIVE: Upon completion of this experiment, students should be able to synthesis potassium tris(oxalate)- aluminate(III) trihydrate. INTRODUCTION: Aluminium (Al) is located in p-block with principal oxidation state of 3+. The Al surface is protected from being oxidized by a layer called aluminium oxide (Al 2 O 3 ). When Al 2 O 3 dissolves in excess hydroxide, the aluminium hydroxide, [Al(OH) 4 ] - ion is formed (eq 1). The addition of oxalic acid, (H 2 C 2 O 4 ) will produce the dioxalatoaluminate ion, [Al(C 2 O 4 )] 3- and subsequently neutralize the excess hydroxide ion, OH - . The [Al(C 2 O 4 )] 3- will be precipitated as potassium salt by addition of ethanol. Al 2 O 3 + 2OH - + 3H 2 O 2[Al(OH) 4 ] - Al + 3KOH + 3H 2 C 2 O 4 .2H 2 O K 3 [Al(C 2 O 4 ) 3 ].3H 2 O + 6H 2 O + 3/2H 2
MATERIALS: Potassium hydroxide, KOH Oxalic acid dehydrate, H 2 C 2 O 4 .2H 2 O Ethanol Acetone Distilled water Ice Aluminium foil Beaker 250mL Graduated cylinder Filter paper Watch glass Hot plate Glass rod Buchner funnel METHODOLOGY: 1. 0.50g aluminium foil that been cut to 1cm

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