Chem 200 lab report 5b - Google Docs PDF

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chem 200. lab report for lab 5b....

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Chem 200-11 Molar Mass of citric acid using titration PROCEDURE Refer back to my pre-lab report on page 12 of my lab notebook. In step 8 we changed it to use a graduated cylinder to measure 25 mL of DI water. CALCULATED DATA 3NaOH (aq) + H3C6H5O7 (aq) → Na3C6H5O7 (aq) + 3H2O (l) g of citric acid used

Trial 1

Trial 2

Trial 3

0.159 g

0.159 g

0.161 g

Burette readings

initial

final

total

outcome

Trial 1

1.79 ml

27.88 ml

26.09 ml

Hot pink

Trial 2

2.52 ml

28.99 ml

26.47 ml

Light pink

Trial 3

1.35 ml

27.18 ml

25.83 ml

Light pink

Moles of NaOH Trial 1

2.48x10^-3 mol NaOH

Trial 2

2.52x10^-3 mol NaOH

Trial 3

2.46x10^-3 mol NaOH

Calculated MW of citric acid Trial 1

192.0 g/mol

Trial 2

189.0 g/mol

Trial 3

196.4 g/mol

Discussion questions

1. I think there were alot of opportunities for error in this experiment. When you are reading the ml of solution off of the burette, you could be off my a few ml. Another way error could go wrong in this experiment is if you measure out too much of the Citric acid, or if you do not terr your measure before measuring out your grams. 2. For question 2a, I think that the standardized NaOH would be lower because since it was in contact with the air, it would have started to release its fumes. This would cause it to become less dense of the NaOH solution. For question 2b, I think it would be the same because it did not have a chance to standardize yet so there wouldn’t be that many chemicals coming off of the NaOH just yet. It might still be slightly lower, but it wouldn't change a lot. 3. If we would have used 50 mL of water, it would have taken more NaOH solution to get the solution to turn pink and that would definitely changed the molar mass of the citric acid. 4. It would be too high because you would be pouring DI water and the NaOH solution into your flask. This would cause you to use more mL of the solution in your burret. You would get a higher final volume and thus would alter your findings for calculating all of your data....