Sofia Diaz
Per. 4 Chem. 10
Mr.West
12 October 2013
Investigation #6 Quantifying Solution Composition
In investigation #6 we worked with a stock of 10ml of .250M of Cobalt(II)Chloride. The ratio was 5 to 10. I diluted 5 milliliters of Cobalt(II)Chloride with 5 milliliters of distilled water into test tube 1. After I took 5ml of test tube 1 and applied it too test tube 2, which had 5ml of distilled water. I repeated this process with test tube 3 and test tube 4 and test tube 5. The concentration levels of the Cobalt(II)Chloride decreased along each test tube, you could tell since each test tube became a lighter shade of reddish pink. The reason to this was because I needed to determine the wavelength and absorption of the colored solution in each solution.
The absorption spectrum(absorption spectra) is used to measure the absorption of radiation as a frequency or wavelength due to the interaction of the substance with the sample. It is used as tool to determine the presence of a particular substance and the quantity of the substance present in the sample or samples, as in this case I have 5 test tubes. The absorption spectrum for cobalt(II)chloride with the color red has a wavelength of 680nm(nanometers). This means that the solution did not absorb a lot of the color red. From the graph we can see that green was absorbed the most which had a maximum wavelength of 551nm(nanometers). Since the green was mostly absorbed, it was not reflected through the sample when hit with light. The absorbance of the cobalt(II)chloride is found first because with that we are able to find out the concentration level by using the formula M1V1=M2V2. For each test tube the concentration levels were different since they each had varying dilutions. After finding the concentration for all 5 test tubes we used logger pro on the computer to create a beer’s law graph. Logger pro then created a linear graph; which showed the relation between the absorbance and concentration of the colored solution. The concentration levels increased when the absorbance wavelengths did. This order established that the concentration and absorbance align to form a quantitative formation. As for the slope, the computer gave it to us as well; it also gives us quantitative information. It would mean .The Cobalt 2+ ion has lost 2 of its valence electrons and 2 chlorine atoms would be needed to balance out the equation.
In the end of this experiment we found out the relation was a linear graph and how similar the increase of the concentration and absorbance were to each other. We find out that the maximum absorbance of the color was green at 551nm and red was the least absorbed by the solution. The serial dilutions were very helpful because they showed us that the concentration was reducing in each test tube that was transferred,