I. Introduction
1. What is colorimetric analysis?
2. What is Beer’s law? How is colorimetry used to determine the concentration of a colored solution?
3. What is a standard calibration curve and how does it relate to the Beer’s Law?
4. What were the objectives of this experiment?
5. Why is it important to determine the purity of aspirin synthesized from previous experiment?
6. What were the two lab techniques used to determine the purity of synthesized aspirin?
7. How was the purity of synthesized aspirin determined by colorimetric technique?
8. Why is the calibration curve important in determining the purity of the aspirin sample?
9. How were percent purity and percent yield of aspirin calculated?
10. What were the chemical and procedural hazards in this experiment and the corresponding safety precautions you implemented to avoid/minimize the risk of these hazards?
II. Results Analysis
A. Data and Calculations
Summarize important results and attach your Data Sheet and Calibration Curve.
B. Discussion
Part I Calibration Curve of Salicylic Acid Standard Solutions
1. What is the purpose of this part of the experiment?
2. How was the calibration curve (graph) created? What were the parameters needed?
3. What was the name and formula of the standard solution?
4. Why were you required to calculate the concentration of the standard solutions? Show a sample dilution calculations.
5. What does the standard calibration tell us?
6. What was the equation of the best fit line (trend-line equation) of calibration curve?
7. How will you use this trend-line equation to determine the purity of aspirin?
Part IIDetermination of Concentration and Purity of an Aspirin Sample
1. How is the amount of salicylic acid present in the sample related to the purity of the aspirin?
2. How many grams of aspirin was present in the final sample aliquot? Show your calculation.
3. What was the absorbance of your aspirin sample?
4. Did your aspirin sample absorbance fall within the calibration curve? Did you have to dilute your sample again?
5. Using the calibration curve from Part I, what was the concentration of salicylic acid in the aspirin sample?
6. How many moles of salicylic acid were in your aspirin sample? Show your calculation.
7. How many grams of salicylic acid were in your aspirin sample? Show your calculation.
8. How many grams of aspirin were in the sample? Show your calculation.
9. What was the percent purity of your aspirin sample? Show your calculation.
Part IIIDetermination of Percent Yield of Aspirin
1. What was your actual yield from Experiment 5?
2. Using the percent purity of the aspirin sample in Part II, what was your corrected actual yield of your aspirin synthesis? Show your calculations.
3. What was the reasons for your low actual yield? Explain briefly based on the purity of your aspirin?
4. What was your aspirin synthesis percent yield? Show your calculations.
III. Conclusions
1. Why is colorimetric technique useful in determining the purity of your synthesized aspirin?
2. What is the impurity in your aspirin sample that allowed you to use the colorimetric technique?
3. Using the percent purity of aspirin and your assigned limiting and excess reactant mole ration in Experiment 5, what are the reasons for your low percent yield?
4. What is the limitation of colorimetric technique in identifying the concentration of solutions?
5. What are the possible causes of errors in this experiment and how to avoid them?
What is the practical application of this experiment? Give an example.
