Chemistry Lab Skills: Aspirin Titration

Accurately weigh an aspirin tablet into a clean dry 250 mL Erlenmeyer flask using an analytical balance. Calculate the mass by taking the difference between the initial weighing bottle reading and the empty bottle reading.

Add approximately 25 mL of pre-chilled 95% ethanol (cooled to about 15°C) to the flask and swirl until the tablet dissolves. Use a glass rod to crush the tablet if needed, then rinse the rod with ethanol before removal.

Add two drops of phenolphthalein indicator to the flask and titrate with standardized sodium hydroxide solution. Record initial and final burette readings to two decimal places; the endpoint is indicated by a pale pink color.

Dispense additional sodium hydroxide equal to the volume used in titration plus 15 mL to hydrolyze the aspirin. Heat the flask on a boiling water bath for 15 minutes without placing it directly on the hot plate.

Remove the flask from the water bath and allow the solution to cool to room temperature. Prepare a burette with standardized HCl solution and add two drops of phenolphthalein indicator if the solution lost its pink color during heating.

Titrate the cooled solution with standardized HCl until the solution turns colorless. Record the exact HCl concentration and initial and final burette readings to two decimal places.