Lab 9 - due to mistakes in calculation or miscalibration of...

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Part 1 In part 1 the Ka value of acedic acid was determined by measuring the titration curve using a pH meter. This was done by measuring pH changes in acedic acid when small amounts of NaOH were added to it. The Ka value was found by graphing the curve then determining the pH at half equivalence point and then using the formula 10^-pH. The value obtained was 2.51x10^-5. The known value is 1.76x10^-5. The obtained value was a little off. CH3COOH + NaOH -> NaCH3COO + OH- Part 2 In part 2 the Ka value of 3 different solutions were determined by measuring the pH values of the solutions. The values obtained were 6.355, 3.33x10^-5, and 3.146x10^- 6. These values were a little off of the actual value of 1.76x10^-5. This is most likely
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Unformatted text preview: due to mistakes in calculation or miscalibration of the pH measuring tool. The measured pH values in this part were 4.9 and 3.7 respectively, and the calculated pH were 5.9 and 3.7 respectively. HA -> H+ + A- CH3COOH -> H+ + CH3COO- Part 3 The measured pH values in part 3 were 7, 1.4, 12.4, 4.5, 4.4, and 4.6 respectively. The calculated values were 7, 1.4, 12.4, 4.5, 4.4, and 4.6. The values matched perfectly in this part. Sources of Error There were several possible sources of error in this lab. Some were incorrect calibrations or malfunctions with the pH measuring device and the solutions not mixing together completely. Also there may have been incorrect calculations and incorrect additions of chemicals....
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This note was uploaded on 03/14/2010 for the course CHEM 109A 109A taught by Professor Aue during the Spring '09 term at UCSB.

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