Expt. 10

Vinegar Analysis

Note: The Molar Concentration of NaOH used for this experiment is .1116 M NaOH

In this experiment, you will determine the percent by mass of acetic acid in vinegar, using volumetric analysis. The acetic acid is titrated with a solution of sodium hydroxide whose concentration is known. A solution whose concentration is known is called a standardized solution. The balanced equation for the titration is given below:

CH₃COOH (aq) + NaOH (aq) → CH₃COONa (aq) + H₂O (l)

Since 1 mol of acetic acid reacts with 1 mol of sodium hydroxide,

Where M_NaOH is the molarity of the sodium hydroxide solution in mol/L and V_NaOH is the volume of sodium hydroxide added from the burette until the end point of the titration, in L. You will use phenolphthalein as the indicator in order to detect the endpoint.

Percent by mass of acetic acid =

You will compare the acetic acid concentrations of one brand of vinegar (Chem Collective).

EXPERIMENTAL PROCEDURE: The experimental procedure listed below has been performed in the laboratory and recorded for your viewing for assistance. Your goal is to use the Chem Collective virtual simulation and perform the experiment below within the simulated laboratory workbench.

1. Make sure that the 250-mL Erlenmeyer flask provided to you is clean and dry on the outside. Weigh the Erlenmeyer flask. Add about 3-mL of one brand of vinegar to the weighed Erlenmeyer flask and weigh it again. Add 2 drops of phenolphthalein indicator to the solution and rinse the wall of the flask with about 20 mL of deionized water.
2. Fill the burette with the NaOH solution, and make sure that the tip of the burette is also filled with solution. Pour about 50 mL of the NaOH solution into the burette and record the initial reading. The burette volume must be read accurately, to ±0.02 mL.
3. Clamp the burette vertically with the tip just inside the mouth of the Erlenmeyer flask and titrate the sample of vinegar. For the titration, slowly add the NaOH from the burette, while swirling the Erlenmeyer flask with the other hand. Add about 1 mL of NaOH into the Erlenmeyer flask and continue until you near the pink endpoint.

Vinegar Analysis Name ________________________________________

DATA: