You have been given a vial containing either maleic acid, C4H4O4, fumaric acid, C4H4O4, or tartaric — Acid-Base Titration Chemistry Question

This is a solid acid titration experiment. Students had to determine the number of moles of NaOH base present given a 0.25M solution, then perform a titration against a weighed sample of the solid maleic, fumaric, or tartaric acid. The endpoint is detected using phenolphthalein as the indicator. All of these solid organic acids have two ionizable protons.

Experimental Plan: An experiment plan had to describe the steps needed to carry out a successful, microscale titration.
Data and Observations: The recording of data and observations needed to include information about the mass of the acid used and the volume of the base used. Where the quantity was obtained by difference, both observations used to determine the amount should be shown. Significant figures had to be used appropriately.
Sample Calculations and Conclusions: Students needed to provide calculations that supported their conclusions.

An example of excellent student work:
Plan: Dissolve a pre-weighed acid sample in distilled water adding two drops phenolphthalein. Fill the 10.0 ml graduated cylinder with .25M NaOH. Add base gradually until a permanent pink color. Record total volume of base used. Repeat.
Data: Acid used: Maleic MM=116.0 g/mol
Trial One: Mass of acid 0.50g, Volume base 34.4 ml
Trial Two: Mass of acid 0.52g, Volume base 35.0 ml
Calculations: Moles acid = mass acid/MM .0043, .0045. Moles base= (liters base x Mbase) .0086, .0088. Mole base/moles acid 2.0, 2.0
Conclusion: For maleic acid, there are two moles of ionizable protons/mol acid. It is diprotic.