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Analysis of Commercial Aspirin Tablets

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No.4 Analysis of Commercial Aspirin Tablets Aims To To determine the mass of acetylsalicylic acid per tablet in a given commercial sample of aspirn (Brand name). Introduction Aspirn, which is chemically named as acetylsalicylic acid, when is hydrolyzed by excess sodium hydroxide solution, produces acetic acid and salicylic acid. The amount of excess sodium hydroxide solution can be found by back titration. Procedure 1. Standardisation of sodium hydroxide solution 25 cm3 ofApproximately 1M NaOH was pipetted into a 250 cm3 volumetric flask and made up to graduation mark with deionized water. 25 cm3 portion of this solution was titrated against standard 0.05M sulphuric acid with phenol red as indicator. The titration was repeated twice and the result was recorded in a table. Standardization of sodium hydroxide solution Titrant 0.05M, Sulphuric acid Analyte Solution obtained in procedure 2 Indicator Phenol red Titration no. (Trial) 1 2 Final volume of Sulphuric acid, cm3 34.50 25.85 44.55 Initial volume of Sulphuric acid, cm3 14.10 6.80 25.85 Volume used, cm3 19.05 18.70 20.40 Mean volume used, cm3 18.88 Standardization of sodium hydroxide solution Titrant 0.05M, H2SO4 Analyte NaOH Indicator Phenol red Titration no. ...read more.


of moles of NaOH used in hydrolysis =0.025mol - 0.019mol =0.006mol 4. The no. of moles of acetylsalicylic acid =0.006mol*1/2 =0.003mol The mass of acetylsalicylic acid =0.006mol*180g mol-1*1/2 =0.54g Conclusion The no of mole and mass of of acetylaslicylic acid present in one tablet of the commercial sample are 0.003mol and 0.54g respectively. Discussion i. Summary of Main Result The no. of moles of NaOH before hydrolysis was found to be 0.025mol. The no. of moles of NaOH left after hydrolysis was found to be 0.019mol. By subtracting 0.019mol from 0.025mol, the no. of moles of NaOH used in hydrolysis was 0.006mol. Since the mole ratio of NaOH to acetylaslicylic acid is 2:1, so no. of moles of acetylaslicylic acid was 0.006mol*1/2= 0.003mol. Thus, the mass of acetylaslicylic acid was 0.003/180g mol-1 = 0.54g. Results Calculated value Literature value found on package of aspirin/given by teacher Molarity of standardized NaOH 1.00M 1.00M Mass of aspirin 0.54g 0.5g ii. Errors Human error - Instruments have their width of markings. The reading observed by experimenters will be affected by the width of markings . ...read more.


Improvement: -Carrying out the experiment a few times so as to take the mean values(except the trial). v. Further investigation -Test for impurities in aspirin tablets through determining the melting points of aspirin tablets or thourgh chromatography. Questions 1. Standard sodium hydroxide solution cannot be prepared by directly dissolving a known mass of sodium hydroxidee solid into water and making up to a certain volume. Why? There may be water being locked in hydrated crystals of NaOH. 2. What was the purpose of simmering the reaction mixture during the hydrolysis of the aspirin tablets? To provide a suitable temperature for the hydrolysis of aspirin to take place. 3. Suggest an alternative to aspirin which can work without simmering the reaction mixture. Direct titration with alkali. As the solution of aspirin in flask is buried in ice for prevention of hydrolysis with alkali, simmering is surely not needed. 4. On what basis would you choose from a variety of brand names when you need this medicine. The concentration of aspirin contained in the medicines. Whether any gas will be produced when aspirin undergoes reactions in our bodies. What are the side effects caused by these medicines. Reference www.wikipedia.com www.rod.beavon.clara.net/err_orig.htm http://www.chemistry-react.org/go/Tutorial/Tutorial_21681.html http://icn2.umeche.maine.edu/genchemlabs/Aspirin/aspirin3.html ...read more.

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