lev's lab #3

lev's lab #3 - Lab #2 Activity 2 Lab Report Lev Gurevich...

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Lev Gurevich 2-10-2011 Title: Finding the wavelength of maximum Absorbance for the carbonate buffer. Purpose/Objective : The purpose of this experiment is to find the wavelength of maximum absorbance of p- nitrophenol at different pH’s, 4, 7, and 10. In order to achieve these pH’s, we put the p-nitrophenol in buffers that had those specific pH’s and resist change, therefore allowing for the p-nitrophenol to have that pH at the time of spectrometer testing. Background: The point of the overall experiment is to find the pKa of p-nitrophenol. We were introduced to Beer’s Law, which gives the direction relationship between concentration and absorbance. A = ε bc or A = abc where A is the absorbance, ε is the molar extinction coefficient, a is the molar absorptivity, b is the length (in cms) through which the light passes in the solution, and c is the molar concentration of the solution. In short, we measure the maximum absorbance of n-nitrophenol at different pH’s, and then find the absorptivity for each pH, and finally calculate the pKa. Method
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lev's lab #3 - Lab #2 Activity 2 Lab Report Lev Gurevich...

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