The Photocatalysed Decomposition of Aqueous Permanganate

Weigh out accurately two 0.300 g of anatase into two petri dishes (7 cm diameter). Pipette 50.0 cm of 0.002 M KMn04 solution into each petri dish. Prepare this solution by 10-fold dilution from 0.02 M KMn04 (filtered through glass wool and standardised). Stir magnetically the suspensions, at a constant speed and irradiate under a low pressure mercury lamp for 30 minutes in mailced reproducible positions. Measure the pH of the 0.002 M KMn04 solution before irradiation. 

Carry out duplicate titrations. Calculate the amount (ie mols) of Kmn04 decomposed. 

Wash the precipitate on the crucible until the washings are not coloured and toen dry the crucible to constant weight at 105 C. Compare the mass of Mn02 obtained in the reaction (ie mass of residue on crucible - 0.600) with the amount of KMn04 decomposed and the change in pH observed. 

Carry out a blank experiment by repeating the procedure without using a solid. After irradiation, filter through filter paper. The result of the titration gives the uncatalysed reaction and should be subtracted from die result obtained previously. 

Repeat using other photocatalysts eg ZnO, rutile and compare the efficimicy of the different catalysts. 

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