Aspirin Lab

Purpose:

(Summarize in your lab book)

The purpose of the lab is determine the ka and the molecular mass of the acid in an aspirin tablet by performing a titration experiment.

Procedure:

(Summarize in your lab book)

1. Obtain one tablet of aspirin. The amount of acid present in it should be on the bottle. Write this value down.

2. Grind the tablet in a mortar and pestle and empty the powdered tablet into a 250 ml beaker.

3. Using 40 ml of a 50% ethanol/water solution, rinse any remaining powder from the mortar and pestle into the beaker. Repeat using a second 40 ml portion of the ethanol solution to be sure all the solid is rinsed out.

4. Add a magnetic stirring bar and place the beaker on a magnetic stirrer. Let it stir for at least ten minutes.

5. While it is stirring, continue with steps 6 & 7.

6. Obtain a sample of 0.1M NaOH. Fill the burette with NaOH.

7. Setup up the logger pro and the pH meter.

8. Create a titration curve by titrating your acid solution with 0.1 M NaOH. Record the pH every 0.5 mL. Continue collecting data until the pH has leveled off above pH of 11.

9. Use analyze interpolate to determine the important points in your graph.

Calculation / Conclusion:

(All your calculations need to be neat and organized. Be sure to identify what you are finding for each number in your lab book and the formula you are using.)

1. Sketch the graph in your lab book. Be sure to label all important points with values and labels.

2. Calculate the Ka (Hint: Use the important points of your graph to help you)

3. Calculate the concentration of the acid (Hint: Use the important points of your graph to help you)

4. Find the moles of acid.

5. Calculate the molecular mass of the acid.

6. Calculate the percent ionization for the acid.

7. Look up the Ka and the formula for the acid in aspirin.

8. Determine percent error of molecular mass and pKa.