Two Components Of An Unknown Mixture Lab Report

The purpose of this experiment was to identify the two components of an unknown mixture through diverse experimental techniques such as recrystallization, extraction, melting point, and acid-base reactions. From this, the group to which these two compounds belong to had to be determined. These groups are: Carboxylic Acids, phenols, and neutrals. By determining the melting points of the two unknown compounds, these values were compared to the values of melting points in the chart and the proper compound was selected. For the case of this experiment, the unknown mixture contained, 4-methylbenzoic acid. The neutral was not determined due to inaccuracies during the experiment.

Introduction: In order to test the purpose- to determine an unknown

These tend to be very strong acids due to physical properties. The pKa values of these acids typically ranges between 4 and 5. Phenols are organic compounds that consist of a hydroxyl group, -OH. These compounds are generally weak acids with a pKa of approximately 10. A good way to show how these kind of molecules work is shown in the below reactions.

Both of these reactions involves an acid reacting with a sodium bicarbonate, NaHCO3. The pKa value of this compound is around 6.4. looking at the first reaction and comparing the pKa values of the carboxylic acid and the sodium bicarbonate, (4-5, and 6.4 respectively), it can be seen that the sodium bicarbonate will act as a base, due to a higher pKa value, and the reaction will proceed to create a conjugate base and acid. On the other hand, looking at the second equation, it is evident that the phenol when reacted with sodium bicarbonate will act as a base. This is due to sodium bicarbonate having a lower pKa value. This example helps show that through acid-base reactions, and the use of a strong base, the type of unknown mixture can be determined to be either a phenol or carboxylic