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In this lab, we will use the sodium hydroxide to determine the percent acetic acid in vinegar using titration.

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Introduction

Introduction: In this lab, we will use the sodium hydroxide to determine the percent acetic acid in vinegar using titration. Materials used: 1. Burette 2. Beaker 3. Vinegar 4. Sodium hydroxide 5. Phenolphthalein 6. Funnel Raw data: Quantitative: Trial # Mass of vinegar (g ±0.01 g) Initial volume of NaOH (mL ± 0.05 mL) Final volume of NaOH (mL ± 0.05 mL) 1 3.70 0.15 13.35 2 3.94 13.35 28.05 3 3.76 28.05 41.15 Qualitative: 1. As we add sodium hydroxide to vinegar with the phenolphthalein the solution instantly turned pink and then instantly turned colorless. 2. As we got closer to equating the moles of H+ Ions with OH- the pink would stop turning into colorless leaving a pale pink color. Data processing: Trial 1: In order to determine the mass of the acid, we have to calculate the moles of acetic acid used, and we can get that by multiplying the volume of sodium hydroxide used by its molarity that we got in the previous lab where we standardized a base. ...read more.

Middle

1. 2. Now for the uncertainty of the final result: 1. 2. This uncertainty is confusing to put next to our result since it is in percentage too, since this 5.80% of 4.70%, I turned value to an absolute value for convenience: 1. So the final result will be: Percent error: According to my sources, the theoretical value of percent acetic acid is between 4% and 6%, I used the average of the values which is 5%. Now we can calculate the final percent error: 1. 2. 3. Applying the calculations for trail 1 and trail 2, we get the following data table: Trial Volume used (mL ± 0.10 mL) Moles of acetic acid Mass of acetic acid Percent acetic acid in vinegar Percent error 1 13.20 0.00290 moles (± 5.53%) 0.174 g (± 5.53%) 4.70% (± 0.273%) 6.00% 2 14.70 0.00323 (5.45%) 0.194 g (±5.54%) 4.92% (± 0.280%) 1.60% 3 13.10 0.00288 (±5.53%) 0.173 g (± 5.53%) 4.60% (± 0.267%) 8.00% I took the average of the values and got: With a percent error of: 1. 2. 3. ...read more.

Conclusion

We can easily fix this by sealing or insolating the reaction by simply covering the burette with a cork and by sealing the beaker that we titrated in with a plastic wrap but leaving a hole for letting the base through. Another thing to consider is the fact the phenolphthalein might have affected the lab. Since this is a weak acid strong base titration, the end point is above 7 pH. The range at which phenolphthalein turns from colorless to pink is from 8.2-10.0. This means that the endpoint was not reached because the phenolphthalein turned pink the lower ranges. This will decrease in the value of volume used thus the moles of acetic acid, which leads to the decrease of the percent acetic acid. We can fix that by doing more trials but with different indicators each time, this will help us determine or verify out endpoints. This makes sense because in trial 2, the value of volume of base used was higher than all trials, and in that trial the solution was not paler than the others, it was violent pink, and we got a better value than the other two trials. ...read more.

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