Determination of the purity of commercial aspirin

3. Data processing:

                        

CH3COOC6H4COOH                NaOH

Mole ratio:                      1                      :             1

Run 1:

% errormass of aspirin =

naspirin (theoretical) =

VNaOH (used) = (23.45 ± 0.05ml) – (12.65 ± 0.05ml) = 10.8 ± 0.1ml

% errorvolume of NaOH used = × 100% = 0.9%

nNaOH = (0.0108 L ± 0.9%) × 0.1 mol/L = 0.00108 mol ± 0.9%

        → naspirin (actual) = nNaOH = 0.00108 mol ± 0.9%

Percent purity =

Run 2:

% errormass of aspirin =

naspirin (theoretical) =

VNaOH (used) = (34.15 ± 0.05ml) – (23.45 ± 0.05ml) = 10.7 ± 0.1ml

% errorvolume of NaOH used = × 100% = 0.9%

nNaOH = (0.0107 L ± 0.9%) × 0.1 mol/L = 0.00107 mol ± 0.9%

        → naspirin (actual) = nNaOH = 0.00107 ± 0.9%

Percent purity =

Run 3:

% errormass of aspirin =

naspirin (theoretical) =

VNaOH (used) = (33.50 ± 0.05ml) – (22.70 ± 0.05ml) = 10.8 ± 0.1ml

% errorvolume of NaOH used = × 100% = 0.9%

nNaOH = (0.0108 L ± 0.9%) × 0.1 mol/L = 0.00108 mol ± 0.9%

        → naspirin (actual) = nNaOH = 0.00108 mol ± 0.9%

Percent purity =

Average percent purity =

4. Conclusion:

The average percent purity calculated is rather high, which is (96 ± 1%), justifying that the aspirin sample is pure. Therefore, the melting point of the aspirin collected from the experiment should be 135-136ºC. We adhered to the instructions correctly, hence, there are only a few systematic and random errors existed during us carrying out the experiment. That is why the percent purity is not 100%.

5. Evaluation:

The errors mentioned above are presented here along with their improvements: