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Acetic Acid in Vinegar Lab Report

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Chemistry

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Experiment 4: Analysis of Acetic Acid in Vinegar
INTRODUCTION
Titration is a method of analysis where a solution of known concentration (standard
solution) is used to determine the concentration of an unknown solution. The known solution
(titrant) is added to a known quantity of the analyte using a buret until the reaction is complete.
The change in color of the added indicator or the change in color of the solution indicates the end
of the reaction, known as the endpoint [1].
Before titration, standardization must be done first. Standardization is the process of
determining the exact concentration of a solution. A standard solution can be prepared by
dissolving a known amount of primary standard, a pure and stable compound with high molecular
weight, in a known volume of liquid [2].
This experiment aims to standardize a solution of NaOH by using a primary standard,
potassium hydrogen phthalate (KPH) and to determine the percentage acidity of a commercial
vinegar.
METHODOLOGY
A. Preparation of 0.10M NaOH solution
To prepare the NaOH solution, approximately 4 grams of NaOH pellets were
weighed using the top loading balance. After weighing, the pellets were then dissolved in
50 mL of water in a 250-mL beaker. After the pellets were all dissolved, the solution was
transferred to the 1-liter volumetric flask. Distilled water was continuously added until the
1-liter mark was reached.
B. Standardization of 0.10M NaOH
Using the analytical balance, 3 samples of KHP with masses between 0.4000 to
0.6000 grams were weighed separately. Two of the samples were each placed in an
Erlenmeyer flask and one was placed in a Florence flask. Each of the sample was dissolved

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by adding 100 mL of distilled water into the flasks. After dissolving, 5 drops of
phenolphthalein indicator was added into the solution.
For titration of the KHP sample, the 50-mL buret was clamped to the iron stand and
was filled with NaOH solution up to the 50 mL mark of the burette. The KHP sample was
titrated with the NaOH solution. The intial and finals readings of the NaOH solution in the
buret were recorded. These steps were repeated for the next two KHP samples. The
molarity of the NaOH solution from each trial was calculated.
C. Determination of Acetic Acid in Vinegar
Three flasks were weighed separately using the analytical balance. Five milliliters
of commercial vinegar were added to each flask. The flasks were weighed again to
determine the weight of the vinegar added. Fifty milliliters of distilled water and 3 drops
of phenolphthalein indicator were added into each of the flask. Each of the vinegar sample
was titrated using the standardized NaOH solution. The flasks were constantly swirled until
the sample became very light pink. The initial and final readings of the NaOH solution in
the buret were recorded. The percent acidity of the vinegar was computed.
RESULTS AND DISCUSSION
Table 1: Data for NaOH Standardization
Trial 1
Trial 2
Trial 3
Weight of KHP
0.4965 g
0.554 g
0.5711 g

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Experiment 4: Analysis of Acetic Acid in Vinegar INTRODUCTION Titration is a method of analysis where a solution of known concentration (standard solution) is used to determine the concentration of an unknown solution. The known solution (titrant) is added to a known quantity of the analyte using a buret until the reaction is complete. The change in color of the added indicator or the change in color of the solution indicates the end of the reaction, known as the endpoint [1]. Before titration, standardization must be done first. Standardization is the process of determining the exact concentration of a solution. A standard solution can be prepared by dissolving a known amount of primary standard, a pure and stable compound with high molecular weight, in a known volume of liquid [2]. This experiment aims to standardize a solution of NaOH by using a primary standard, potassium hydrogen phthalate (KPH) and to determine the percentage acidity of a commercial vinegar. METHODOLOGY A. Preparation of 0.10M NaOH solution To prepare the NaOH solution, approximately 4 grams of NaOH pellets were weighed using the top loading balance. After weighing, the pellets were then dissolved in 50 mL of water in a 250-mL beaker. After the pellets were all dissolved, the solution was transferred to the 1-liter volumetric flask. Distilled water was continuously added until the 1-liter mark was reached. B. Standardization of 0.10M NaOH Using the analytical balance, 3 samples of KHP with masses betw ...
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