Theoretical Background
What is vinegar and what does it contain?
Vinegar is a sour-tasting, clear liquid that freezes below 62 °F. It is known as White
Vinegar, Ethanoic Acid, or Acetic Acid. It is an organic chemical compound that consists
mostly of acetic acid (CH3COOH) and water (H2O). It is made naturally and synthetically,
through the oxidation of Ethanol in an alcoholic liquid.
The methods that can be used to analyze the content of vinegar.
The easiest method to determine the acid content of vinegar would be a process known
as the Acid Base Titration Analysis. Here, an identified volume of HCl would be measured
with a graduated cylinder and titrated with a solution of NaOH of known molarity.
Afterward, the solution would be added slowly until all the acid is neutralised. To accurately
measure the volume of NaOH used, the exact amount of NaOH required to neutralised must
be known. This can be done using an acid-base indicator, otherwise known as
Phenolphthalein, which is colourless in acidic solutions but turns pinkish in a basic solution.
By following these procedures, the acid content of the vinegar can be found.
Titration- what is it? How does it work?
Titration is a laboratory technique used to determine the concentration of an unknown
reagent using a standard concentration of another reagent that reacts chemically with the
unknown reagent. The standard solution would then be referred to as the ‘titrant’. It works
by adding a specific reactant to the solution until it is neutralised. The whole point is to
determine the amount of reactant required to neutralise or bring the solution to a known
pH.
Indicator- what is it? How does it work?
An indicator is a weak (usually organic) acid that changes its molecular shape with
changes in pH. As the shape changes, so does the colour of the solution. Phenolphthalein
has a figure below pH8, and is virtually colourless. At a pH above 8, however, the shape
changes and turns to a shade of pink. Therefore it is colourless in acid and pink in a base,
which can be used to determine the acidity of solution.
Equivalence point and end point – what are they?
The equivalence point is the point where the number of moles of base equal the
number of moles of acid. The end point is the point where the used indicator changes
colour, otherwise known as the ‘indication point’.
Hypothesis: My hypothesis is that based on this research, the higher the concentration of
the vinegar inside the solution, the higher the concentration of Ethanoic Acid will be. This is
given that the concentration of the Sodium Hydroxide is kept fixed.
Data Collection
Organized Raw Data
Vinegar (ml) H2O (ml)
0.5
1
1.5
2
2.5
50
50
50
50
50
NaOH (ml)
Trial 1
Trial 2
Trial 3
8.1
8.2
10
26.7
24
19
27.5
27.5
27.2
35.7
31
34.7
50.5
47.8
44.4
Table 1: Title
Data Processing
Write the Chemical Equation
CH3COOH + NaOH  CH3COONa + H2O
Calculation from Chemical Equation
Table 2: Title
NaOH Vol (dm3)
0.0081
0.0082
0.01
M (NaOH) Mol (NaOH)
1
0.0081
1
0.0082
1
0.01
0.0267
0.024
0.019
1
1
1
0.0267
0.024
0.019
0.0275
0.0275
0.0275
1
1
1
0.0275
0.0275
0.0275
0.0357
0.031
0.0347
1
1
1
0.0357
0.031
0.0347
0.0505
0.0478
0.0444
1
1
1
0.0505
0.0478
0.0444
Vinegar Vol (dm3)
0.5
0.5
0.5
Average
1
1
1
Average
1.5
1.5
1.5
Average
2
2
2
Average
2.5
2.5
2.5
Average
Mol (Vinegar)
0.0081
0.0082
0.01
Vinegar Solution Vol (dm3)
0.0505
0.0505
0.0505
0.0267
0.024
0.019
0.051
0.051
0.051
0.0275
0.0275
0.0275
0.0515
0.0515
0.0515
0.0357
0.031
0.0347
0.052
0.052
0.052
0.0505
0.0478
0.0444
0.0525
0.0525
0.0525
M (Vinegar)
0.16
0.16
0.20
0.17
0.52
0.47
0.37
0.46
0.53
0.53
0.53
0.53
0.69
0.60
0.67
0.65
0.96
0.91
0.85
0.91
Data Presentation
Graph 1: Concentration Chart
1.2
1
0.8
Trial 1
0.6
Trial 2
Trial 3
0.4
0.2
0
0.5
1
1.5
2
2.5
Graph 2: Concentration Graph
0.8
0.7
0.6
0.5
Trial 1
0.4
Trial 2
Trial 3
0.3
0.2
0.1
0
0.5
1
1.5
2
Explanation
Analyzing Results
Based on the results attained, it proves that the more the Vinegar in a solution, the
higher the concentration of the Ethanoic acid will be. This completely supports the original
hypothesis. The experiment was also done in 3 trials for each amount of vinegar, which
means that results are generalised. Based on the concentration graph, Trial 3 has the best
and clearest result. There no anomalies, as all the results make perfect sense. Results show
that as the amount of the vinegar inside the solution increase, as does the concentration of
the Ethanoic Acid. The experiment was done with a fixed amount of Phenolphthalein,
Water, and a fixed concentration of Vinegar and Sodium Hydroxide. There were no
anomalies, because as seen in the table, chart, and graph, the concentration of the Ethanoic
Acid never decreases if the volume of the Vinegar inside the solution is increased. This is
because the amount of water is kept at a fixed volume, but the volume of the vinegar varies.
Evaluation
Method Evaluation
The method of the experiment was very good. It was executed properly as well. For
future reference however, this experiment was done in a rush. Though done carefully as to
attain proper results, it would be better to take things at a considerably slower pace next
time, to even better ensure accuracy.
Data Reliability
Data presented is very reliable. All note takings were done cautiously and carefully so
that the data collected would be accurate. All calculations were double checked to make
sure it is accurate. The formula was taken directly from notes taken in class. Balancing the
formula was also done carefully. Everything, no matter at what pace, was done with careful
work, so results are most likely to be accurate and reliable. No anomalies present.
Conclusion
The conclusion here is that based on the data collected, processed, and presented, it’s
fair to say that the higher the amount of Vinegar in a solution, the higher the concentration
of the Ethanoic Acid. It is most clearly shown with the graph, trial 3. It has a steady
inclination, proving the steady increase in concentration of Ethanoic Acid. During the
experiment, 2 batches of NaOH were used. That was the only problem and uncertainty
faced during the procedures. Hopefully though, the concentration of NaOH was exactly the
same for both batches. Otherwise anomalies might have shown and would be identified.
Other than that, the method seems practical, logical, reasonable, and reliable.
Perhaps next time a good research question would be to find out what would happen
should the concentration of NaOH be altered during the experiment. Still, from this
experiment, the concluding statement would be that the concentration of Vinegar is directly
proportional to the concentration of Ethanoic Acid. This supports the hypothesis, and
evidence supporting conclusion is presented in the table, chart, and graph.
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