Name_________________________ Date_________ Period________
acids and bases lab 2
Percentage of acetic acid in vinegar by titration Introduction Vinegar is a mixture of acetic acid (C2H4O2) and water. Is it mostly water, or mostly acetic acid? In this experiment we will find the percent acetic acid in vinegar by mass. Since acetic acid is an acid, it will react with a base. The more base it takes to neutralize the acetic acid, the higher the concentration of acetic acid. This principle is known as titration: Assaying the concentration of an acid or base by neutralizing it. Procedure 1. Fill a buret with 1M NaOH and record the initial volume:____ 2. Add exactly 25 mL of vinegar and 3 drops of phenolphthalein to a flask and place it under the buret. 3. Drip in the 1M NaOH while stirring until the solution just becomes permanently pink. Record the final volume:_____ Total NaOH added: _____ mL (trial 1) 4. Perform a second trial Total NaOH added: ____ mL (trial 2) Average volume NaOH added:______________ mL 5. Calculate the Molarity of the vinegar using the titration formula:
Molarity of unknown =
molarity of known x liters of known liters of unknown
(This equation is true only when the known and unknown react on a equimolar basis, which is true in this case) For this experiment we can rewrite the formula:
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