postlab10 - solution is diluted. The first part we added a...

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Sam Eichenblatt November 11 th , 2009 Chem 1310 A2 Post lab discussion 10 For the first part of the lab an unknown acid was titrated with a strong base to find the identity of the acid. The ph was recorded of the solution every .5 ml of base added. As expected the solution eventually exceeded the buffer zone and the pH jumped from 5.78 to 11.1. The equivalence point was at 33 mL of base with a pH of 8.16. This is how the acid was identified. It only had one pKa value so the choices were automatically limited to acetic acid or benzoic acid. The pKa was calculated by taking the half way point between the equivalence point and zero; this identified the pKa as 4.6, very close to the pKa of acetic acid of 4.5. The second part of the experiment tested what would happen to the solution when strong acids and strong bases were added. It also tested the buffer capacity of acetic acid and what would happen when the
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Unformatted text preview: solution is diluted. The first part we added a strong base, NaOH. The pH only increased .11 because the solution is buffered. Then the strong acid was added, HCl. Again the pH only dropped slightly, from 4.66 to 4.5, because the solution is buffered. Then NaOH was added until the buffer capacity was exceeded. Because of the low amount of acetic acid in the solution it only took a very small amount of NaOH to exceed the buffer. The capacity was found by taking the difference between final pH and initial pH and dividing by two. This gave the midpoint in the difference. Then the midpoint was added to the initial to find the buffer capacity. The final part water was added to acetic acid. The pH decreased which means that more H+ was formed. This is because more acetic acid dissociated when there was more water to break the bonds in the acid....
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This note was uploaded on 09/07/2010 for the course CHEM 1310 taught by Professor Cox during the Fall '08 term at Georgia Tech.

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