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Unformatted text preview: Verina Atalla PHS 2301- 7:30- 10:25 AM Title: Pipetting techniques and photometry Partner name: Christina L. Purpose/Objective: The purpose of this experiment is to calculate the pKa of p- nitrophenol (a weak acid) using the Beers Law equation and the Henderson- Hasselbalch equation. Background: Beers Law is an equation we use to show the relationship between concentration and absorbance. A = bc or A = abc A is absorbency, is the molar extinction coefficient, a is the molar absorbtivity, b is the length that the light passes through the solution (in centimeters), and c is the molar concentration of the solution. We are using the molar absorbitivity to find the pKa of p-nitrophenol. Method: Look in lab procedure manual Results : Table 1 Absorbance values for p-nitrophenol at pH 10 at 370-430 nm values Wavelengt h cuvette Absorbance cuvette Absorbance 370 CB blank CS .447 380 CB blank CS .544 390 CB blank CS .652 400 CB blank CS .662 410 CB blank CS .659 420 CB blank CS .522 430 CB blank CS .362 The...
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This note was uploaded on 03/09/2011 for the course PHS 2301 taught by Professor Bohu during the Spring '11 term at St. John's.
- Spring '11