Percentage Yield Lab Report

1)
Percentage yield experiment: First we measured 20cm3 of sulphuric acid into a beaker using a measuring cylinder, this will help us determine the percentage yield at the end of the experiment. We then heated the beaker containing the sulphuric acid using a Bunsen burner in order to heat it up for the copper oxide to mix with. We then weighed out 1.02g of copper oxide and added it to the acid and stirred it whilst doing so, we did that until the liquid turned blue, this proves that the chemicals have mixed together. We then weighed this liquid which will help us determine the percentage yield. We then filtered the liquid off which gave us the amount we obtained. We then left the liquid for a week so that the liquid had time to turn into crystals,

We then added 10cm3 ethanoic anhydride to the salicylic acid and swirled the contents, this mixes together the two chemicals. We then added 5 drops of concentrated sulphuric acid to the flask and thoroughly swirled the mixture, this creates the solution that makes the aspirin. We then warmed the flask for 20 minutes in a 400cm3 beaker of hot water which was approximately 60°C, we made sure the flask did not go above 65°C because this could have caused the contents to evaporate. Part 2: Using a 25cm3 measuring cylinder we measured out 15cm3 of ethanol into a boiling tube and then prepared a beaker half filled with hot water at approx. 75°C, we got this temperature by filling the beaker with cold water and slowly adding boiling water from a kettle until we reached the right temperature. We then used a spatula to add the crude aspirin to the boiling tube and placed the tube in the beaker of hot water, and stirred it so that it will dissolve into the ethanol. We then poured the hot solution containing dissolved aspirin into approximately 40cm3 of water in a 100cm3 conical flask, the solid did not separate so we did not need to warm the contents of the flask in the water bath. We then let the conical flask cool slowly so that the white needles of aspirin separated. We did have crystals so we did

We then used a small mortar and pestle to crush the aspirin and we placed the resulting powder into a conical flask, we crushed the aspirin tablets so that I would be easy to mix with the ethanol. We then added 5ml of ethanol using a measuring cylinder and covered the flask with a watch glass, we did this to avoid evaporation. We then gently heated the mixture over a water bath of around 60-70°C and swirled frequently, we did this so that it would dissolve the acetylsalicylic acid. We then filtered off the hot solution to remove any insoluble material in another small conical flask, we rinsed the flask with a few ml’s of chilled ethanol to collect any residue that was left on the flask. We then slowly added 25ml of chilled deionised water to the filtrate to initiate crystallization by using a measuring cylinder and a dropping pipette, once we had done this we left it for about 10 minutes to allow crystallization at room temperature. We then weighed a filter paper which we will use later in the experiment. We then collected the crystallized acetylsalicylic acid by vacuum filtration in a Buchner funnel and washed the product with a little ice-cold water. We then pre-weighed a clean, empty watch glass and labelled it with our initials and the date, we did this do we could easily identify that it was ours when we go to weigh it with the crystals on. We