Chemistry Help!?? We did an experiment in lab and measured the absorbance and tr

Question

Chemistry Help!??

We did an experiment in lab and measured the absorbance and transmittance for the following compounds, and I don't understand how to write the chemical equations or why the colors are different. For each, write the chemical equation for it's dissociation in water.... What must account for the different colors?

- Co(NO3)2 Absorbance- 0.012, transmittance- 98.6%

- Cu(NO3)2 Absorbance- 0.987, trnasmittance- 10.39%

- Ni(NO3)2 Absorbance- .003, tansmittance- 99.99%

Also confused about this, we constructed a calibration curve using standards ranging from 0.019 M Cu(NO3)2 to 0.10 M Cu(NO3)2. If I had a Cu(NO3)2 solution of unknown concentration and was asked to analyze it, how would I analyze it? The unknown solution has a concentratoin between 0.14 M and 0.19 M.

Explanation / Answer

- Co(NO3)2 ---> Co+2(aq) + 2NO3-(aq)

- Cu(NO3)2 --> Cu+2(aq) + 2NO3-(aq)

- Ni(NO3)2 --> Ni+2(aq) + 2NO3-(aq)

the color change is essentially to the presence of the metal ion... Co´2, Cu+2 and Ni+2

You could analyse this by:

- Potentiometric titration

- colorimetry

- gravimetry

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