testing the purity of aspirin
...ution) is added from a burette to a known quantity of the analyte (the unknown solution) until the reaction is complete. Knowing the volume of titrant added allows the determination of the concentration of the unknown. Often, an indicator is used to usually signal the end of the reaction, the endpoint. The indicator I shall use is phenolthalein, which shall go pink when the solution is neutralized. This is the point where you measure the titration at. I shall use sodium hydroxide to titrate the solution as it is an alkali and it will neutralize the aspirin which is an acid. Equipment list: Conical flask-to mix the solutions Beaker-containing 1.5g aspirin, 85ml water & 85ml ethanol Burette-containing NaOH, accurate to the nearest 0.1ml which is important for the reliability of the answer Clamp stand-important to hold the burette in place Funnel-to avoid spillages Measuring cylinder-accurate to the nearest degree, important for measuring both the sodium hydroxide and the acetylsalicylic acid. Phenolthalein-to show when the titration is at it’s endpoint Safety: Insert safety cards What I did: Firstly the aspirin that I made earlier was dissolved into a solution, not only by water but also by ethanol as acetylsalicylic acid is a weak organic acid that is not extremely soluble in water so the ethanol increases solubility. The measurements are as follows: 1.5g of aspirin 85 ml of water 85 ml of ethanol Then I transferred this solution to the conical flask ready to place under the burette. I then filled the burette with 50ml of NaOH, and removed any air bubbles. Then place the conical flask under the burette and slowly add the alkali to the acid. Swirl the flask as you add it to make sure it is all thoroughly mixed. Placing the flask over a piece of white paper will help to see any colour change. When the solution turns a pale pink it has reached the end point so you take a reading from the burette and record it. Repeat this 5 times for fair testing. Titration number Titration result, ml 1 17 2 16.9 3 17 4 17.4 5 17 Average titration = (17+16.9+17+17.4+17) = 17.06 5 Analysis: C6H8O4 Molecular mass = 180g ...