PERCENTAGE OF ACETIC ACID IN VINEGAR PDF

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Summary

Lab report on finding the percentage of acetic acid in vinegar...

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Mita Ray CHEM0950-3 Feb 15, 2021 LAB 1

ABSTRACT The objective of this lab is to accurately determine the weight percentage of acetic in a bottle of vinegar. Having his accuracy in percentage is important as federal law requires vinegar to contain at least 5% acetic acid by weight. This can be achieved by titrating vinegar with titrating vinegar with a standardized 0.1 M NaOH solution. The mean of NaOH added in the three trials is 40.02 mL, the standard deviation is 0.527, the relative standard deviation is 1.32%. The mean of acetic acid percentage is 6.41%, the standard deviation is 0.132, the mean percent error is 28.1%, the relative standard deviation is 2.07%.

INTRODUCTION Procedures and Instruments

A titration is a controlled reaction performed using a known concentration and an unknown concentration. In this experiment, the titrant is 0.1 M NaOH and the unknown concentration to be analyzed is vinegar. Using a pipette, transfer 5 mL of vinegar into a 250 mL Erlenmeyer flask. Using a 50 L buret, NaOH is carefully added to vinegar with phenolphthalein drops on a stir plate until a pink color is consistently observed in the solution in multiple trials.

Equations

1. The reaction in this titration is NaOH + CH3COOH → H2O + CH3COO- + Na+.

2. Percentage of acetic acid in vinegar can be calculated with (g acetic acid / g vinegar) x 100%. 3. Standard deviation is (std)= sqrt((∑(value−mean)^2))/  N 4. Confidence interval is mean ± texp* std / (√n) 5. Relative standard deviation is standard deviations/mean*1000

RESULTS / DISCUSSION TITRATION RESULTS Trial

NaOH (mL)

% Acetic Acid in Vinegar

Moles NaOH

1

40.21

6.445

0.004021

2

40.42

6.515

0.004042

3

39.42

6.259

0.003942

The mean of NaOH added in the three trials is 40.02 mL, the standard deviation is 0.527, the relative standard deviation is 1.32%. The mean of acetic acid percentage is 6.41%, the standard deviation is 0.132, the mean percent error is 28.1%, the relative standard deviation is 2.07%.

ACETIC ACID DENSITY Trial

Vinegar (g)

Vinegar (mL)

Density (g/mL)

1

4.983

5

0.9966

2

4.977

5

0.9954

The mean of the density is 0.996 g/mL, the mean of the mass is 4.98 g, the standard deviation is 0.004, the relative standard deviation is 0.09%.

ANALYSIS OF ERROR The data in Table 1 is precise, but not accurate. It has a significant mean percent error of 28.1%. The values of Table 2 are both fairly precise and accurate. A source of error may be attributed to adding too much NaOH to the vinegar, resulting in a saturated pink color.

CONCLUSIONS The average weight percentage of acetic acid in vinegar is 6.41% so it can be determined with 95% accuracy that the weight percent of the acetic acid will be between 6.259 and 6.515. The vinegar fails the T table test since it was determined that it does not contain 5% vinegar with 95% certainty. However, this may be attributed to errors within the experiment. The G(calc) is 0.199, there were statistical outliers.

REFERENCES Halmi, T. A. Analyzing the Acid in Vinegar. http://chemistry.bd.psu.edu/halmi/chem3vinegars05.pdf

Stubbings, J. Acid-base Titration Curve Calculations (Strong Monoprotic Acid-Strong Base). https://www.ausetute.com.au/titrcurvcalc.html...