Postlaboratory Problems And Questions

*1. Upon UV illumination and in the absence of air, a photocatalytic phenomenon occurs in a suspension containing Ti02 + dissolved copper (II) acetate, (CUC4H6O4) which simultaneously yields the following products (see Reiche, 1979):

a) A metallic deposit (A)

b) A gas (B) that produces a white precipitate upon bubbling in a saturated lime solution (CaO)

c) A gas (C), which upon elemental analysis is shown to be a saturated hydrocarbon. When subject to partial oxidation, this gas generates an acid that contains the same anion present in the initial suspension.

With this information, write:

ii) The main (balanced) reaction that occurs at:

I. The semiconductor site acting cathodi-cally:

II. The semiconductor site acting anodi-cally:

(Note: Ac" is the acetate anion) III. The global reaction

With this information, a) Write the balanced oxidation and reduction reactions, and the global reaction (without electrons or holes in it).

b) Would you expect a pH change during the global process? Explain.

Notes:

ii. The recombination of an electron and a hole brings about their "neutralization" in the sense that this process does not yield any substance but only energy.

iii. A hole can be understood as a "virtual species" in such a way that A + h+ = A+. On the other hand, A + e" - A-.

3. Calculate the theoretical number of moles of C02 produced from the oxidation of the organic species used in the experiment (assuming a 100% yield).

* Answer in this book's webpage at www.springer.com

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