Investigatory Project Report
Measurement of Acetic Acid in Vinegar
Introduction
This project aims to determine the percentage of acetic acid present in vinegar using the
titration method. Acetic acid (CH₃COOH) is the main component that gives vinegar its
sour taste. The concentration of acetic acid can be determined by titrating it with a base
of known concentration, such as sodium hydroxide (NaOH).
Aim
To measure the amount of acetic acid in vinegar using acid-base titration.
Materials Required
• Vinegar sample
• 0.1 M NaOH solution
• Phenolphthalein indicator
• Burette, pipette, conical flask, funnel
• Distilled water
Theory
Titration is a method used to determine the concentration of a substance by reacting it
with a solution of known concentration. In this case, acetic acid reacts with sodium
hydroxide:
CH₃COOH + NaOH → CH₃COONa + H₂O
One mole of acetic acid reacts with one mole of NaOH.
Procedure
1. Fill the burette with 0.1 M NaOH solution.
2. Use a pipette to take 10 mL of vinegar and transfer it to a conical flask.
3. Add 2-3 drops of phenolphthalein indicator to the vinegar.
4. Titrate by slowly adding NaOH from the burette while swirling the flask.
5. Stop when the solution turns light pink and the color remains.
6. Note the volume of NaOH used.
7. Repeat the titration to get consistent readings.
Observations and Calculations
Volume of vinegar taken = 10 mL
Average volume of NaOH used = 16.5 mL
Molarity of NaOH = 0.1 M
Moles of NaOH = 0.1 × 0.0165 = 0.00165 mol
Moles of CH₃COOH = 0.00165 mol (1:1 reaction)
Concentration of CH₃COOH = 0.00165 / 0.010 = 0.165 M
Mass of acetic acid = 0.00165 × 60 = 0.099 g
Percentage of acetic acid = (0.099 / 10) × 100 = 0.99%
Result
The vinegar sample contains approximately 0.99% acetic acid.
Conclusion
By performing an acid-base titration using sodium hydroxide as the base and
phenolphthalein as the indicator, the amount of acetic acid in vinegar was successfully
measured. The experiment demonstrated the practical use of titration in determining
concentrations of unknown solutions.