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andrade7 - EXPERIMENT 7 BUFFER LAB(INFORMAL Pre-Lab...

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EXPERIMENT 7: BUFFER LAB (INFORMAL) Pre-Lab Questions ( 5 points each ): ___5___ / 10 pts Data: ___10___ / 10 pts Table containing pH data from Experiment 1. This table should include the theoretical pH values, the actual measured pH values, and the pH values after correctly preparing the buffer solutions. (5 points) Table containing all pH values for all 7 acetic acid/acetate solutions. (5 points) Sample Calculations: ___5___ / 5 pts Buffer Capacity Calculation (5 points) Results: ____14__ / 16 pts Plots of measured pH vs. Drops (HCl or NaOH) added for each of the 7 buffer solution. Plots must be properly labeled and constructed. Plots must also contain linear regression and the equation of the lines for each. Conclusion: ___7___ / 7 pts ___41___ / 48 pts Question 1: 2 pts Question 2: 2 pts Question 3: 5 pts Question 4: 10 pts Question 5: 4 pts Question 6: 5 pts Question 7: 5 pts Question 8: 5 pts Question 9: 10 pts Style (organization, spelling, grammar, neatness, etc…) __4____ / 4 pts Deductions (i.e., Late Lab Report, incorrect formatting, spelling etc.) - ______ Total Score __86____ / 100 pts
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Preparation and Investigation of Buffers Francisco Andrade Jessica Booe Travis Kirkpatrick 5/13/10 Wesley Storm CHEM 241L 402, Morehead Labs Room 301
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Pledge In the first part of Experiment 1, 100mL of an acetate buffer with a pH of 5.00 that was 2.00M in acetic acid was prepared from liquid acetic acid and sodium acetate 1 . The literature values for the pK a and density of liquid acetic acid are 4.756 and 1.049, respectively 1 . From this information, the volume of liquid acetic acid and the mass of sodium acetate can be determined. Sample calculations are shown below. Volume of acetic acid: mL g mL mol g L L cid molacetica 14 . 1 049 . 1 1 1 05 . 60 1 1 . 0 1 200 . 0 = acetic acid Mass of sodium acetate: [ ] [ ] weakacid ase ConjugateB pK pH a log + = M x M x M x M x 351 . 0 , 200 . 0 . 10 , 200 . 0 log 244 . 0 , 200 . 0 log 76 . 4 00 . 5 244 = = = + = g mol g L L mol M 76 . 4 1 08 . 136 1 1 . 0 1 35 . 0 35 . 0 = = sodium acetate In the second part of this experiment, a buffer was prepared by partially neutralizing a weak acid with a strong base. The 100mL acetate buffer of pH 5.00 that is 0.200M in acetic acid was to be made with only pure liquid acetic acid and 1.0M NaOH. In order to find the volume of NaOH, the following was calculated: HA + OH - A - Initial 0.02mol 0 0 Change -x +x +x Equilibrium 0.02-x 0 x
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x x pK pH a - + = 02 . 0 log x x x x x x x x - = = - = - = - + = 02 . 0 754 . 1 02 . 0 10 , 02 . 0 log 244 . 0 , 02 . 0 log 756 . 4 5 244 . mL L x x x x x x 7 . 12 0127 . 0 , 554 . 2 0350 . 0 , 754 . 1 0350 . 0 , ) 02 . 0 ( 754 . 1 = = = = - = - Experiment 1 Data: The following table illustrates the data obtained by preparing a buffer solution three different ways. The most accurate method was the “correct way,” which is the procedure that is usually followed and was the procedure followed in the third part of the experiment
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This document was uploaded on 11/04/2011 for the course CHEM 241 at UNC.

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andrade7 - EXPERIMENT 7 BUFFER LAB(INFORMAL Pre-Lab...

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