A clear colourless liquid, highly corrosive, very toxic, fatal if inhaled, highly reactive, reacts violently with water. Potential burns, risk of inhaling toxic gases and cause inflammation or burns. To avoid any accidents use the fume cabinet for all uses of sulfuric acid. Precautions such as wearing goggles, gloves and lab coats. Heating mantle Could cause burns if touched or if dropped the damage to one’s foot Sensible footwear must be worn in the labs to avoid any hurt. When transferring the product in the flask, be careful the glass has cooled down.
Glass As all equipment such as the round bottom flask, the glass rod, beakers etc will be made from glass it will be easy to break and could hurt somebody. To avoid unnecessary accidents all equipment should be handled with care, and each step should be completed thoroughly and carefully. Wear sensible footwear in the labs to avoid any bleeding, in addition do not run in the lab. Thermometer As thermometers have slight volumes of mercury in them they must be handled with care. If drop poisonous toxins could be realised.
To avoid any breakages of the thermometer do not leave on any surfaces unattended. Place in flask at all times, and if needed to be removed unscrew to loosen the thermometer but still place and retighten the thermometer back in to flaskThe experiment consisted of heating the salicylic acid, with the acetic anhydride. Cold water is added after the reaction, after adding 750ml of cold water, a white precipitate was formed since aspirin is insoluble in cold water; this step is necessary for the purification of the crystals and avoids any impurities.
The results collected for the melting point showed the crystals started to melt at 119°c which then completely finished melting at 122°c. The mass of wet product was 82. 82g and the mas of the dry product was 52. 39g and the mass of the theoretical yield is 65. 22g. Finding these results made it possible to calculate the percentage yield which was 80. 56%. As the experimental objective was to produce Aspirin, measure the melting point but also in addition to this the amount of yield collected meant the procedure was successful.
The yield calculated was very high and showed the experiment is feasible and as Aspirin is already produced in industry this confirms how the yield collected from each batch will always have minimal loses. However as the percentage yield was not closer to 100% there are still ways in which more sample could have been collected and stop any aspirin from going to waste. Firstly during suction filtration procedure, Aspirin was left behind on the Buchner funnel and filter paper. As they were quite small particles it was very tricky to try and remove each grain of aspirin.
To avoid this we could allow time for the filter paper and sample to dry then slowly remove the left over product. However this would take time to do and slow down the experiment. Extra product could also be lost during the dissolving and recrystallization. Ethanol was used to dissolve the crystals, as well as the impurities including salicylic acid. When cold water is added after the entire product has been dissolved, not all may have reformed consequently some may need cooler water to become insoluble. To try and avoid this trying colder temperatures of water could be used.
The salicylic acid and acetic anhydride that didn’t react are all dissolved by the addition of ethanol. As this reaction is Endothermic, using Le Chatliers principle; the presence of excess acetic anhydride would cause a favoured forward reaction and want the desired product. Although if reactants do not react enough the product made would still be minimal, and misused by being dissolved and not completely reacting. Another source of error was the weighing scale which is sensitive to air movement and easily fluctuates the mass measured, thus would create an increased amount of errors that would build up.
Therefore to avoid mini errors, weighing the substance should be done in a non-drafted area. A source of error would be the apparatus which measured the melting point which would have limited accuracy, hard to control the temperature and rate of melting, along with this experiment being very complex any unforeseen variables that are hard to control or cannot be controlled may pop up. The equipment used will have left over product on them, which would be a potential source of error and a low the yield. Such as trying to transfer all the sample from the round bottom flask in to the beaker, or residue left on the glass rod.
Again some errors are unavoidable and are just minimised as in this situation. Measuring the melting point came to 135°C (Haynes, 2014) but the experimental melting point was 122°C. The melting points show a small range, but a larger difference between the theoretical and actual melting points. There can be many reasons as to why there was a difference between the melting points. As the yield is not 100% some of the product may have been lost when transferring the product from one container to another.
All reactants may not have all reacted. Conclusion The experiment as a whole was successful and the reactants react together to form Aspirin, however if the experiment was to be done again a way to increase the percentage yield would make it feasible would make the experiment more commendable. For example when measuring the melting point the temperature there should be more control over the temperature and humidity of the surroundings, and kept at a minimum to stop the reactants reacting with vapour in the air.