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Aspirin tablets

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Introduction: Aspirin is an analgesic and antipyretic drug. Analgesics are drugs which relieve pain. Antipyretics are drugs which lower body temperature. The main constituent of aspirin tablets is 2-ethanoyloxybenzoic acid. Aspirin passes unchanged through the acidic condition and the stomach but is hydrolysed to ethanoate ions and 2-hydroxybenzoate ions by the alkaline juices in the intestines. CH3COOC6H4COOH + 2OH? � CH3COO? + HOC6H4COO? + H2O Salicylates lower body temperature rapidly and effectively in feverish patients, but have little effect if the temperature is normal. They are also mild analgesics, relieving certain type of pains, such as headaches and rheumatism. Although the toxic dose from salicylates is relatively large, their uncontrolled use could be dangerous. Single dose of 5 to 10 grams of salicylates have caused death in adults, and 12 grams taken over a period of twenty-four hours produces symptoms of poisoning. Principle: The object of this experiment is to determine the percentage of 2-ethanoyloxybenzoic acid in aspirin tablets. A known amount of standard sodium hydroxide solution is used in excess to hydrolyze known mass of aspirin tablets. ...read more.


4. 4. Safety glasses were worn. 5 The mixture was cooled and transferred with washings to a 250cm� standard flask and was made up to the mark with distilled water. Part 3 : Estimate the quantity of unused NaOH after the hydrolysis 1. 25cm� of the hydrolysed solution was transferred by a pipette into a conical flask. 2. The solution was titrated against 0.0962M hydrochloric acid using phenolphthalein indicator. Data/Observation: Part 1: Titration number Trial 1 2 Initial burette reading/ cm� 0.40 14.90 0.20 Final burette reading/ cm� 25.10 39.30 24.60 Titre/ cm� 24.70 24.40 24.40 Mean Titre/ cm� (24.40+24.40)/2 = 24.40 Part 3: Titration number Trial 1 2 Initial burette reading/ cm� 0.70 0.30 5.50 Final burette reading/ cm� 7.70 7.00 12.20 Titre/ cm� 7.00 6.70 6.70 Mean Titre/ cm� (6.70+6.70)/2 = 6.70 1. Molarity of standard hydrochloric acid = 0.0962M 2. Mass of 3 aspirin tablets = 1.76g 3. The color of indicator changed from red to pink in both titration. 4. The aspirin tablets were white in color. 5. The aspirin tablets dissolved in sodium hydroxide solution to give a colorless solution. ...read more.


The solution which is hot and contain corrosive sodium hydroxide will spill out if we boil it vigorously. 3. What might the remainder of the tablets be made of? The tablets might be made of some acidic impurities. Source of errors: 1. The aspirin tablets may contain more than one kind of acid, titration of the aspirin will neutralize not only the 2-ethanoyloxybenzoic acid. 2. The aspirin tablets may not fully dissolve in the distilled water and sodium hydroxide solution. 3. The mixture of aspirin solution may not be well-shaken. 4. Extra drops of hydrochloric acid may added while the end-point is reached since the end-point is difficult to detect. 5. The space between the tip of burette and the tap may not filled with solution before titration. 6. Some solution may stick on the tip of burette. 7. It was not easy to get a good estimation to 0.05 cm� from the burette. 8. Some solution may evaporate and escape while heating. Precaution: 1. Hydrochloric acid and sodium hydroxide is corrosive. We should avoid contacting the solution with our skin. 2. Safety goggles must be worn during heating and titration. 3. The solution should be heated gently to prevent it from spilling out. 4. We should wash our hands after the experiment. ...read more.

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