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Zinc oxide and Cu (1 Viewer)

lepton_index

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Syllabus point: Explain the relationship between absorption and reflectance spectra and the effect of infra-red and ultra-violet light on pigments including zinc oxide and those containing Cu

I'm fine with explaining the relationship between absorption and reflectance spectra --- but I can't find any information on ZnO and Cu effect. Please help,

Thanks
 
R

randhi

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Okay this is some stuff from my notes:

- IR(heat) can change the colour of zinc oxide in the presence of oxygen from white to yellow. Copper(I)Oxide (red) turns to Copper(II)Oxide (black).
- TiO2 a white pigment doesn’t change colour.
-Infrared spectra utilizes a ceramic heat source to pass IR through a sample and solvent, and then compare the relative intensities, which allows the absorption of radiation to be determined. IR changes colour of ZnO2 in the presence of O2 from white when cold to yellow when hot. Cu2O goes from red to black CuO.
 

nit

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Some other things you could talk about are copper tetraammine and how the concentration of a solution of this may be determined by shining uv at it, since absorbance is directly proportional to concentration...ie uv can be used for quantitative measurements of a copper solution; for infra-red radiation, you could possibly mention emerald green (containing copper and arsenic) that absorbs some ir wavelengths and hence shows up dark when infrared radiation is shone at it, and the reflected ir recorded by some type of data-logger.
 

lepton_index

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Thanks. I got it. And just a quick note: for the "explanation" bit: Bbcause the electrons in the Zn and Cu atoms absorb UV / IR, so their electron configuration in the outermost shell are changed, thus they change colour.
E.g.: Zn is white when cold, because its outermost shell is filled. But it is yellow when hot - indicating that the 3d subshell is not fully occupied.
 

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