Titration Experiment
Background Information: Phenolphthalein (phen) is an indicator that is colorless in an acid and bright pink in a base.

Purpose: To determine the molarity of three acids – citric acid, vinegar, and soda.

Hypothesis: Before you begin the experiment, hypothesize. Predict which substance will have the highest molarity? The lowest?

Procedure:

1. Add 10 drops of acid to a clean, rinsed cup. Add 1 drop of phen, the indicator.

2. Add 0.1 M NaOH, drop by drop to the acid until the color turns pink.

3. Record the number of drops of NaOH needed to reach neutralization.

4. Rinse and dry the cup before going onto the next trial.

If time allows, repeat each experiment twice.

Data:

 Number of drops of 0.10 M NaOH Trial #1 Trial #2 10 drops of citric acid 10 drops of vinegar 10 drops of soda

The balanced equations for the reactions:

Citric acid:  H3C6H5O7 + 3 NaOH  3 H2O + Na(C6H5O7)3

Vinegar:      HC2H3O2  + 1 NaOH H2O + NaC2H3O2

Soda:         H2CO3  + 2 NaOH   H2O + Na2CO3

Data Analysis:

Find the molarity of each acid.

Conclusion: All three of these acids are weak, but obviously, they vary in strength. Rank them from least to most acidic.

E Saylor

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