• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

The objective of this experiment is to calculate the % purity of aspirin, by first neutralizing the acetylsalicylic acid with excess sodium hydroxide, and then back titrate the excess

Extracts from this document...

Introduction

The titration of aspirin Objective : The objective of this experiment is to calculate the % purity of aspirin, by first neutralizing the acetylsalicylic acid with excess sodium hydroxide, and then back titrate the excess base with standardised hydrochloric acid. Apparatus : burette, pipette, volumetric flask, funnel. Procedure : 1) About 1.5 gm of aspirin was accurately weighed, the mass was recorded. 2) The weighed amount of aspirin was transferred into a beaker , 25 cm3 of 1 molar NaOH was then transferred into the beaker. The beaker was then gently heated for 10 minutes. 3) After heating, the solution was then transferred into a volumetric flask via a funnel. More distilled water was then added to the flask to make a final volume of 250 a cm3. ...read more.

Middle

7) The above titration is repeated 3 times, and the result is recorded. Result and Calculation: Mass of aspirin = 1.504 gm Concentration of NaOH = 1 mole/L Concentration of HCl = 0.1 mole/L Reaction after adding of NaOH is : 2H2O 1 mole of aspirin will react with 2 moles of NaOH Reaction for the titration is : NaOH + HCl ==> NaCl + H2O 1 mole of NaOH will react with 1 mole of HCl The result of the titration is tabulated as follows: Burret Reading Titration 1 Titration2 Titration Final Reading 9.2 16 25 Initioal reading 0 7.0 16 Volume used 9.2 9 9 % purity 94.55% 95.74% 95.74% Calculation : Sample calculation using result of titration 2 # moles of HCl use = Molarity * Volume in litres ...read more.

Conclusion

Of the above only 0.09 moles was left behind, so the aspirin has reacted with 0.025 - 0.009 = 0.016 moles of NaOH. 1 mole of aspirin will react with 2 moles of NaOH So the number of moles of aspirin must be 0.016/2 = 0.008 moles Molecular mass of aspirin (C9H8O4) = 180, so mass of acetylsalicylic acid = 0.008 * 180 = 1.44 g So % purity of aspirin = (1.44/1.504) * 100 = 95.74% The other titration results was calculated the same way. Average purity = 1/3 (94.55 + 95.74 + 95.74) = 95.34% Conclusion and discussion: The error in this lab is in the judgement of the end-point, in which the solution will completely becomes colourless. The result was quite consistent, the average % purity is 95.34% ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Aqueous Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Aqueous Chemistry essays

  1. Marked by a teacher

    ANALYSIS OF ASPIRIN BY BACK TITRATION

    4 star(s)

    Hydrochloric acid (0. l mol/dm3) Aspirin tablet Bromocresol Purple indicator Deionised water A commercial aspirin tablet was placed into a 250cm3 conical flask with a magnetic stirrer bar Then sodium hydroxide solution (0.1mol/dm3, 60cm3)

  2. Preparation of aspirin - The chemical background This is the overall reaction that ...

    Alcohols can be esterified either by using an acylating agent or by reacting with a carboxylic acid in the presence of an acid catalyst. Salicylic acid and Ethanoic acid-mechanism: This mechanism is similar to the general formation of an ester.

  1. Titrating Sodium hydroxide with an unknown molarity, against hydrochloric acid to find its' molarity.

    corrosive, wear eye protection2 As, when using any corrosive of dangerous chemicals, lab coats should be worn in order to protect clothing and skin. Care should be taken when handling these chemicals and any spillages should be dealt with immediately.

  2. Determining the purity of Iron Wool.

    Using a funnel 0.02 mol dm-3 potassium manganate VII solution was poured into a burette up to 0.00cm3 mark and titrated until a permanent overall pink-ish colour change occurred. This reading was noted and the titration portion of the experiment was carried out two more times with all readings noted and the average of them used in the final calculations.

  1. Investigating different types of aspirin and making aspirin.

    Chromatography Mobile phase Stationary phase Thin-layer Liquid solvent Al2 03 or Si 02 (often bounded together with CaSo3 and supported on a plastic sheet or glass plate this is called a TLC plate) Paper Liquid solvent H20 can the surface of absorbent chromatography paper and therefore support by the cellulose fibres in paper)

  2. Making Aspirin.

    However, those studies were not supported by sufficient physical data to prove the existence of these forms. Based on this history and the importance of this molecule, researchers studied its potential for polymorphs using Accelrys' C2.Polymorph, commonly known as the Polymorph Predictor.

  1. Investigation in to discover the percentage of acetylsalicylic acid in a sample of aspirin ...

    Despite its usefulness, there is a danger to taking too many aspirin. Over time aspirin can cause gastronomical bleeding that leads to iron deficiency, and also gastric ulcers may occur. They should not be given to children as it increases the risk of contracting Reye's syndrome, a serious and often fatal disease of the brain and some abdominal organs.

  2. the synthesis of azo dyes, aspirin and soap

    The reaction takes place under 10�C to prevent the NN, the N2 diazonium ion decomposing into N2 gas. This suggests that the delocalization of the diazonium ion bond electrons over the benzene ring is only able to stabilize the diazonium salt at cold temperatures.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work