Unknown Diprotic Acid Through Titration

Determining the Identity of an Unknown Diprotic Acid Through Titration
Kevin S. Burton; Madison Gallegos
April 2, 2018

Abstract

There is more than a single way to determine the molar mass of a compound or element. Titration is one such way to determine molar mass by reacting an unknown compound or element with a known compound or element. In this experiment an unknown diprotic acid was combined with a known base, in this particular case, NaOH. As it was known to be diprotic, the unknown acid was to give two H+ ions in a chemical reaction with the known base. This knowledge allowed for a balanced chemical equation for the titration to be created:H2X+2NaOH2H2O+Na2X. At the start of the experiment there was an amount of acid, of which the

Any minor error in the measurement of how much acid was used, or the amount of base let into the solution, would cause the calculated molar mass values to be higher or lower depending on the miscalculation. If the solid diprotic acid had not been fully dissolved in DI water by the the time the Phenolphthalein indicated a complete neutralization reaction had taken place, the amount of NaOH needed will be erroneously low. If that happens in one of the trails for the experiment, the calculated molar mass would be incredibly high. If the color of the solution when the trial is finished is a dark pink color, that would show that the solution was too basic, and too much NaOH was added. Adding too much of the NaOH base to the solution would cause the calculated molar mass for the acid to be erroneously low. There are however some aspects of the experiment that could be changed with little to no effect on the color of the solution or the calculated molar masses. For instance, if the amount of deionized water used were to be doubled, there would be no change in the results of the titration calculations. This is the reason that the amount of DI water used in this experiment was not measured nor

Determining when exactly the titration was complete was based entirely on the color of the solution. Reaching the titration equilibrium may have been difficult solely from the patience and concentration it took to recognize when to stop adding the base solution. Because the color was observed by every individual running the experiment, there is bound to be variations on the stopping points. In order to help neutralize the solution entirely, carbon dioxide was added to the solution in the form of a breath. It is difficult to measure the amount of carbon dioxide in a breath, and therefore may have led to incorrect calculated