Lab 4 / Titration for Acetic Acid in Vinegar

Purpose / IntroductionThis lab will produce a simple method to determine the concentration of an acetic acid

through the use of titration with a basic solution and an indicator; the indicator used in this lab will be phenolphthalein: colorless in acid, pink or red in base. Normally the concentration of a solution is determined by molarity; however, when titration is used normality is preferred. To determine the normality of the acetic acid the following equation will be used

Nacid=(N base ) (Volumebase )

Volumeacid Once the concentration of the acetic acid is calculated, the weight percent can be calculated. To calculate the weight percent of the acetic acid the mass of the acid must be calculated: the product of the acid normality and the acid's gram-molecular-weight. Then the following equation can be used to find the weight percent

% Acid=(Massacid gLρvinegar)×100

It is assumed the density of vinegar is 1000gL

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I expect this lab to produce the following results. First, the addition of NaOH to the vinegar and phenolphthalein solution will create a color change of colorless to pink or red once the neutralization point is breached. The acetic acid's calculated weight percent of the provided vinegar should be somewhere between 4% and 8%.

Materials and MethodsA data table is created to record the quantity of NaOH needed to neutralize a volume of

acetic acid. The set up for this lab requires a setup of items –books, LabPaq box, etc.– to elevate the syringe used for the titration setup. The titrator for this lab will be made from a syringe and stopcock, and the syringe will be kept upright with the test-tube clamp. The beaker will be placed below the titration setup with a piece of white paper underneath to observe color changes. The syringe will be filled with NaOH , and a few drops should be passed through the titrator to remove air from the stop cock tip. Thoroughly wash the beaker with soap and water, and dry completely.

Record the initial volume of NaOH in the syringe. Measure out a volume of vinegar with the graduated cylinder, and transfer it to the beaker. Add a couple drops of phenolphthalein solution to the vinegar in the beaker. Place the beaker underneath the NaOH titrator. Adding one drop of NaOH to the vinegar and phenolphthalein solution, swirl and observe any color changes in the beaker. Repeat this step until the colorless solution becomes pink or red for an extended period of time. Once the solution changes color record the remaining volume of NaOH in the titrator.

Pour the beaker solution down the drain, and thoroughly wash and dry the beaker. Repeat the titration process two more times to obtain two more sets of data. Once complete, pour the solutions down the drain, and clean and dry thoroughly. Wipe down lab area as well.

Safety

For this experiment goggles should be worn. If NaOH comes in contact with skin, wash with soap and water.