Here is the revised organic chemistry practical report: Experiment 3: Preparation of Aspirin (Acetyl Salicylic Acid) 1. Objective To synthesize aspirin (acetylsalicylic acid) from salicylic acid and acetic acid via an esterification reaction, and to determine its percentage yield and melting point. 2. Materials Salicylic acid (1.5 g) Acetic acid (6 mL) 85% Sulfuric acid or Phosphoric acid (catalyst) Distilled water (20 mL + for recrystallization) Conical flask Water bath Ice bath Heating plate Filter funnel Filter paper Beakers Thermometer Weighing balance 3. Procedure 1. Salicylic acid (1.5 g) was placed into a clean conical flask. 2. Acetic acid (6 mL) and a few drops of 85% sulfuric acid or phosphoric acid (catalyst) were added to the flask. 3. The mixture was heated in a water bath at 90 °C for 3 minutes. 4. The flask was removed from the water bath. While the mixture was still hot, distilled water (20 mL) was added. 5. The flask was allowed to stand at room temperature until crystallization began. 6. The flask was cooled in an ice bath to maximize crystal formation. 7. The crystals were filtered using a Büchner funnel or gravity filtration. 8. The crude aspirin was recrystallized by dissolving it in a minimum amount of hot water, then cooling to allow pure crystals to form. The product was filtered and dried. 9. The dried, purified aspirin was weighed to determine the actual yield. 10. The melting point of the purified aspirin was determined using a melting point apparatus. 4. Reaction Equation The synthesis of aspirin involved the esterification of salicylic acid with acetic acid, catalyzed by a strong acid. $$ \text{C}_7\text{H}_6\text{O}_3 \text{ (Salicylic Acid)} + \text{C}_2\text{H}_4\text{O}_2 \text{ (Acetic Acid)} \xrightarrow{\text{H}_2\text{SO}_4/\text{H}_3\text{PO}_4} \text{C}_9\text{H}_8\text{O}_4 \text{ (Aspirin)} + \text{H}_2\text{O} \text{ (Water)} $$ 5. Calculations Molar Masses: Salicylic acid ($\text{C}_7\text{H}_6\text{O}_3$): $138.12 \text{ g/mol}$ Acetic acid ($\text{C}_2\text{H}_4\text{O}_2$): $60.05 \text{ g/mol}$ Aspirin ($\text{C}_9\text{H}_8\text{O}_4$): $180.16 \text{ g/mol}$ Moles of Reactants: Moles of salicylic acid: $$ \text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}} = \frac{1.5 \text{ g}}{138.12 \text{ g/mol}} = 0.01086 \text{ mol} $$ Moles of acetic acid (assuming density of acetic acid $\approx 1.05 \text{ g/mL}$): $$ \text{Mass} = \text{Volume} \times \text{Density} = 6 \text{ mL} \times 1.05 \text{ g/mL} = 6.3 \text{ g} $$ $$ \text{Moles} = \frac{6.3 \text{ g}}{60.05 \text{ g/mol}} = 0.1049 \text{ mol} $$ Limiting Reactant: The reaction ratio between salicylic acid and acetic acid is 1:1. Since $0.01086 \text{ mol}$ of salicylic acid was less than $0.1049 \text{ mol}$ of acetic acid, salicylic acid was the limiting reactant. Theoretical Yield of Aspirin: Based on the limiting reactant, the theoretical yield of aspirin was: $$ \text{Theoretical Yield} = \text{Moles of Salicylic Acid} \times \text{Molar Mass of Aspirin} $$ $$ \text{Theoretical Yield} = 0.01086 \text{ mol} \times 180.16 \text{ g/mol} = 1.956 \text{ g} $$ The theoretical yield of aspirin was $\boxed{\text{1.96 g}}$. Percentage Yield: To calculate the percentage yield, the actual yield (mass of purified aspirin obtained experimentally) is required. $$ \text{Percentage Yield} = \frac{\text{Actual Yield (g)}}{\text{Theoretical Yield (g)}} \times 100\% $$ (Note: Actual yield data is needed to complete this calculation.) 6. Results Theoretical Yield: 1.96 g* Actual Yield: (To be determined experimentally)* Percentage Yield: (To be calculated after determining actual yield)* Melting Point of Aspirin: (To be determined experimentally)* The expected melting point for pure aspirin is approximately $135 \text{ °C}$. A lower or broader melting point range would indicate impurities. 7. Discussion The synthesis of aspirin involved an esterification reaction. The strong acid catalyst protonated the carbonyl oxygen of acetic acid, making the carbonyl carbon more electrophilic and susceptible to nucleophilic attack by the hydroxyl group of salicylic acid. Heating accelerated the reaction. The addition of water after heating helped to precipitate the aspirin, as aspirin is less soluble in water than salicylic acid. Cooling in an ice bath further enhanced crystallization. Recrystallization from hot water was crucial for purifying the crude product, removing unreacted starting materials and byproducts. The percentage yield indicated the efficiency of the synthesis, while the melting point provided an assessment of the purity of the synthesized aspirin. 8. Recommendations Accurate temperature control: The water bath temperature should be precisely maintained at 90 °C to optimize reaction rate and prevent side reactions. Thorough drying: The synthesized aspirin should be completely dry before weighing to obtain an accurate actual yield and percentage yield. Residual water will inflate the mass. Purity verification: A ferric chloride test should be performed to confirm the absence of unreacted salicylic acid, which would indicate incomplete reaction or insufficient purification. Waste disposal: All chemical waste should be disposed of according to laboratory safety guidelines. That's 2 down. 3 left today — send the next one.