Relative Molecular Mass of Aspirin:
Mass of carbon: 12.011 g/mol
Mass of oxygen: 15.999 g/mol
Mass of hydrogen: 1.0079 g/mol
Mass of Aspirin: 9 (12.011) + 4 (15.999) + 8 (1.0079) = 180.1582 +/- 0.0000 g/mol
Theoretical Yield of Aspirin:
Mass of Salicylic Acid: 1.0167 +/- 0.0001 g
Relative Molecular Mass of Salicylic Acid: 138.1216 g/mol
Relative Molecular Mass of Aspirin: 180.1582 g/mol
Theoretical Yield: 1.0167g x (1 mol/138.1216 g) x (1 mol aspirin/1 mol salicylic acid) x (180.1582 g/mol) = 1.3261 +/- 0.000001 g
Actual Yield of Aspirin:
Mass of Filter Paper: 0.6499 +/- 0.0001 g
Mass of Filter Paper and Aspirin: 1.2305 +/- 0.0001 g
Actual Mass of Aspirin: 1.2305 – 0.6499 = 0.5806 +/- 0.0002 g
Percent Yield:
Actual Mass of Aspirin: 0.5806 +/- 0.0002 g
Theoretical Yield of Aspirin: 1.326127 +/- 0.000001 g
Percent Yield: (0.5806/1.326127) x 100 = 43.7816 +/- 0.0002 %
Propagation of Uncertainties:
Relative Molecular Mass of Salicylic Acid:
Mass of carbon: 12.011 g/mol
Mass of oxygen: 15.999 g/mol
Mass of hydrogen: 1.0079 g/mol
Mass of Salicylic acid: 7 (12.011) + 3 (15.999) + 6 (1.0079) = 138.1216 +/- 0.0000 g/mol
Uncertainty: 0.000/12.011= 0.000
0/7 = 0.00
0 + 0 = 0
0/100 x 84.077 = 0.00
0.0000/15.999 = 0.00
0/3 = 0
0.00 + 0 = 0.00
0.00/100 x 47.997 = 0.00
0/1.0079 = 0
0/6 = 0
0 + 0 = 0.00
0.00/ 100 x 6.0474 = 0.00
0.00 + 0.00 + 0.00 = 0.0000
Relative Molecular Mass of Aspirin:
Mass of carbon: 12.011 g/mol
Mass of oxygen: 15.999 g/mol
Mass of hydrogen: 1.0079 g/mol
Mass of Aspirin: 9 (12.011) + 4 (15.999) + 8 (1.0079) = 180.1582 +/- 0.0000 g/mol
Uncertainty: 0.000/12.011= 0.000
0/9 = 0.00
0 + 0 = 0
0/100 x 108.99 = 0.00
0.0000/15.999 = 0.00
0/4 = 0
0.00 + 0 = 0.00
0.00/100 x 63.996 = 0.00
0/1.0079 = 0
0/8 = 0
0 + 0 = 0.00
0.00/ 100 x 8.0632 = 0.00
0.00 + 0.00 + 0.00 = 0.0000
Theoretical Yield of Aspirin:
Mass of Salicylic Acid: 1.0167 +/- 0.0001 g
Relative Molecular Mass of Salicylic Acid: 138.1216 g/mol
Relative Molecular Mass of Aspirin: 180.1582 g/mol
Theoretical Yield: 1.0167g x (1 mol/138.1216 g) x (1 mol aspirin/1 mol salicylic acid) x (180.1582 g/mol) = 1.326127 +/- 0.000001 g
Uncertainty: 0.0001/1.0167 = 0.000098357
0.0000/138.1216 = 0.0000
0/1 = 0
0/180.1582 = 0
0.000098357 + 0.00 + 0.00 + 0.00 = 0.000098357
0.000098357/100 x 1.326127 = 0.000001
Actual Yield of Aspirin:
Mass of Filter Paper: 0.6499 +/- 0.0001 g
Mass of Filter Paper and Aspirin: 1.2305 +/- 0.0001 g
Actual Mass of Aspirin: 1.2305 – 0.6499 = 0.5806 +/- 0.0002 g
Uncertainty: 0.0001 + 0.0001 = 0.0002
Percent Yield:
Actual Mass of Aspirin: 0.5806 +/- 0.0002 g
Theoretical Yield of Aspirin: 1.326127 +/- 0.000001 g
Percent Yield: (0.5806/1.326127) x 100 = 43.7816 +/- 0.0002 %
Uncertainty: 0.0002/ 0.5806 = 0.0003445
0.000001/1.326127 = 0.0000007541
0.0003445 + 0.0000007541 = 0.000345
0.000345/ 100 x 43.78 = 0.0002
Questions:
- Relative Molecular Mass of Salicylic Acid:
7 (12.011) + 3 (15.999) + 6 (1.0079) = 138.1216 +/- 0.0000 g/mol
Relative Molecular Mass of Aspirin:
9 (12.011) + 4 (15.999) + 8 (1.0079) = 180.1582 +/- 0.0000 g/mol
Theoretical Yield of Aspirin:
1.0167g x (1 mol/138.1216 g) x (1 mol aspirin/1 mol salicylic acid) x (180.1582 g/mol) = 1.3261 +/- 0.000001 g
Actual Yield of Aspirin:
1.2305 – 0.6499 = 0.5806 +/- 0.0002 g
Percent Yield:
(0.5806/1.326127) x 100 = 43.7816 +/- 0.0002 %
- Material would be lost at Stage 1 in the transferring of the acetic anhydride and sulfuric acid into the flask from the graduated cylinder and pipette. In Stage 2 of the reaction, material may have been left in the flask while filtering. This could have been corrected by placing more water in the flask and filtering until all of the solid product was on the filter paper. Losses could be minimized by using apparatus in place of the flask that already has measurement on it. The apparent yield might be too large if there was any salicylic acid leftover as well as water, acetic anhydride or sulfuric acid. If there was leftover reactant such as salicylic acid, the limiting reactant, the reaction may not have come to completion due to not enough catalyst. If there was any excess water of aqueous solution in the final product, the product may not have been given enough time to drain the solution and liquid.
- The main impurities in the sample would be salicylic acid, ethanoic anhydride and water.
