A student prepares acetylsalicylic acid (aspirin) by reacting salicylic acid with ethanoic anhydride in the presence of a phosphoric acid catalyst. The student starts with 6.90 g6.90\text{ g}6.90 g of salicylic acid (Mr=138.0M_r = 138.0Mr=138.0). After the reaction, the student obtains aspirin as an impure solid. The student purifies the solid to obtain 6.12 g6.12\text{ g}6.12 g of pure aspirin (Mr=180.0M_r = 180.0Mr=180.0).
Describe a method to obtain a pure sample of aspirin from the impure solid, calculate the percentage yield of this preparation, and describe how the student could check the purity of the final product.
