CHM!2201! Fall!2008! Department!of!Chemistry!Organic!Chemistry Lab I Villanova University Extraction, Distribution Coefficient Experiment 4A Calculation Worksheet A. Prepare the Standard Benzoic Acid Solution 1. Calculate the molarity of your standard Benzoic Acid (PhCO2H; Molecular Weight: 122.12) solution: 0.61g PhCO2H x 1 mole PhCO2H = .005 mole PhCO2H dissolved in 250 mL water Benzoic Acid 122 g PhCO2H (PhCO2H) M.W. = 122.12 .005 mole PhCO2H = X mole PhCO2H Solve for X: X = 0.02 mole PhCO2H in 1000 mL water or 0.02 M PhCO2H 250 mL water 1000 mL water B. Single 10 mL Extraction and Determination of Distribution Coefficient 1. Calculate amount of Benzoic Acid you are starting with: 50 mL 0.02M PhCO2H x 0.02 mole PhCO2H x 122.12 g PhCO2H = 0.122 g PhCO2H in starting aqueous solution. 1000 mL 0.02M PhCO2H 1 mole PhCO2H 2. To calculate amount of PhCO2H remaining in aqueous solution after extraction with 10 mL of methylene chloride, titrate aqueous layer with 0.02M NaOH ____mL 0.02M NaOH x 0.02 mole NaOH x 1mole PhCO2H x 122.12 g PhCO2H = Y g PhCO2H remaining in aqueous layer 1000mL 0.02M NaOH 1 mole NaOH 1 mole PhCO2H 3. Calculate the amount of PhCO2H extracted into the methylene chloride layer 0.122 g PhCO2H - Y g PhCO2H = Z g PhCO2H in 10 mL methylene chloride extract 4. Calculate Kd Kd = C methylene chloride = Z g PhCO2H / 10 mL = Z / 10 = Calculated Kd C water (Y g PhCO2H) / 50 mL Y / 50 (Continued on other side) Page - 1 - of 2CHM!2201! Fall!2008! Department!of!Chemistry!Organic!Chemistry Lab I Villanova University Page - 2 - of 2 Experiment 4A Calculation Worksheet (continued) C. Two 5 mL Extractions 1. Calculate amount of Benzoic Acid (PhCO2H) you are starting with: 50mL 0.02M PhCO2H x 0.02 mole PhCO2H x 122.12 g PhCO2H = 0.122 g PhCO2H in starting aqueous solution. 1000 mL 0.02M PhCO2H 1 mole PhCO2H 2. To calculate amount of PhCO2H remaining in aqueous solution after extraction with 2 x 5 mL of methylene chloride, titrate aqueous layer with ~0.02M NaOH ____mL 0.02M NaOH x 0.02 mole NaOH x 1mole PhCO2H x 122.12 g PhCO2H = Y g PhCO2H remaining in aqueous layer 1000mL 0.02M NaOH 1 mole NaOH 1 mole PhCO2H 3. Calculate the total amount of PhCO2H extracted into the 2 x 5 mL methylene chloride layers 0.122 g PhCO2H - Y g PhCO2H = Z g PhCO2H total amount in 2 x 5mL methylene chloride extracts _________________________________________________________________________________________________________________________________ 4. Calculate theoretical amount of PhCO2H that should be removed by 2 x 5 mL metheylene chloride extractions using Kd calculated in Step B4. For the first 5 mL extraction with methylene chloride where W is the amount of benzoic acid extracted into methylene chloride: Kd = C methylene chloride = W g PhCO2H / 5 mL = W / 5 = Calculated Kd (value determined in B4) C water (0.122 g PhCO2H - W g PhCO2H) / 50 mL (0.122 – W) / 50 ( Kd = known quantity; solve equation for W). Repeat this calculation for the second 5 mL extraction using the W value determined above and where A is the amount of benzoic acid extracted into the second 5 mL portion of methylene chloride: Kd = C methylene chloride = A g PhCO2H / 5 mL = A / 5 = Calculated Kd (value determined in B4) C water (0.122 g PhCO2H - W g PhCO2H – A g PhCO2H) / 50 mL (0.122 – W – A) / 50 (W, Kd = known quantities; solve equation for A). Combine calculated W and A values to get theoretical amount of acid removed by two 5 mL extractions and compare with the amount experimentally found. TMBare