• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  9. 9
  10. 10
  11. 11
  12. 12
  13. 13
  14. 14

Analysing the ethanoic acid concentration in different types of vinegars.

Extracts from this document...


Analysing the ethanoic acid concentration in different types of vinegars. Vinegar is a mixture of various acids, ethanoic acid being the most abundant. Most vinegars are made from a sugary liquid, this liquid is fermented to produce ethanol and then oxidised to form ethanoic acid. Different vinegars use different sugary liquids and this could lead to variation between the vinegars. My aim in this investigation is to discover whether the concentration of ethanoic acid varies between vinegars. Vinegar consists mostly of water (bp = 100 degrees C) and ethanoic acid but it also contains many flavour components and other acids in low abundances. From my research I have discovered that the main acids in Vinegar are: Citric Acid C6H8O7 mp = +153 degrees C Tartaric Acid C4H6O6 mp = +170 degrees C Malic Acid C4H6O5 mp = +101-103 degrees C Succinic Acid C4H6O4 mp = +183 bp = +235 degrees C Ethanoic Acid C2H4O2 mp = +16.6 bp = +117.9 degrees C Phosphoric Acid H3O4P mp = +158 degrees C Proponic Acid C3H6O2 bp = + 141 degrees C Due to all the other acids contained in vinegar I will not be able to obtain my results for the concentration of ethanoic acid direct from the vinegar, as the H+ ions produced by the other acids will effect the results of my titrations. Therefore I need a way of separating the ethanoic acid from the solution of vinegar. I will do this via the process of fractional distillation. This is a process whereby different substances in a solution are separated from one another. It is done by heating the solution in a round-bottomed flask and as the solution begins to warm up different substances contained within the solution begin to boil off. This gas is then condensed into a liquid using the condenser and can be collected. Using a thermometer you can measure the temperature it boils off at and as each substance has its own unique boiling point you can tell what substance you are collecting. ...read more.


Ka of ethanoic acid = [CH3CO2-]eqm x [H+]eqm [CH3CO2H]eqm From my equation I know that [CH3CO2-]eqm = [H+]eqm, and also from my research I know the Ka value for ethanoic acid = 1.7 x 10-5. Hence I can now write my equation in this form. 1.7 x 10-5 = [H+]eqm2 [CH3CO2H]eqm 1.7 x 10-5 = (3.162 x 10-3)2 [CH3CO2H]eqm [CH3CO2H]eqm = (3.162 x 10-3)2 1.7 x 10-5 [CH3CO2H]eqm = 0.588 (3 sf) Now I have obtained my values for X and X-Y however to get the concentration of ethanoic acid my distillate (Y) I will need to add the two values together. [CH3CO2H] in vinegar (Y) = 0.588 + 3.162 x 10-3 = 0.591 (3sf) Therefore the values obtained from my pH meter for all my distillates is that the concentration of ethanoic acid = 0.591 mol/dm3. Now using the measurements I took of the volume produced by the distillation of the vinegar I can calculate the concentration of ethanoic acid in Vinegar. Vol. Of Malt Vinegar distillate = 47.5 cm3 Vol. Of Cider vinegar distillate = 47.9cm3 Vol. Of White wine vinegar distillate = 48.1cm3 Concentration of ethanoic acid in vinegar = Volume of distillate/ volume of vinegar x concentration of ethanoic acid in distillate. Malt vinegar = 47.5/50 x 0.591 = 0.561 mol/dm3 Cider vinegar = 47.9/50 x 0.591 = 0.566 mol/dm3 White wine vinegar = 48.1/50 x 0.591 = 0.569 mol/dm3 Also So I will be able to compare the pHs of my distillates with that of my original acid I took 3 pH readings for all of my original acids and averaged them. Malt vinegar = pH 3.0 Cider vinegar = pH 3.0 White Wine Vinegar = pH 2.8 During my experiment I used a number of techniques to try and ensure the results I obtained were as reliable and accurate as possible. Despite this it is very likely that qualitative and quantitative errors have had an effect on the accuracy of my results. ...read more.


Two of my vinegars have identical pHs and these vinegars have similar concentrations of ethanoic acid (both 0.7 to 1 dp) whereas the values for the concentrations of other organic acids vary relitivly significantly. The pHs of all my distillates were the same. This is surprising as my titration results showed that the concentrations of ethanoic acid in the distillates varied significantly. This could be due to the limited accuracy of the equipment as the pH meter can only measure to 0.1 and so may not be able to pick up subtle differences in the pHs of the distillates. Or it could be due to the fact that this method contains a lot of quantitative error that could of affected my results. As you can see from the analysis I have been able to make trends in my results and most of them fit these trends. However as you can see by the differences between the two values for the concentration of ethanoic acid I obtained, there is clearly error in my results. However the results from both the methods seem to fit in with my scientific knowledge and as I haven't obtained any anomalous results I believe that my results are fairly accurate. However there are improvements I could make to my method to improve accuracy. Instead of measuring out the vinegar in a measuring cylinder next time I would measure it out using a pipette as it is far more accurate. Also during titrations I would invert the burette to make sure that the NaOH does not collect towards the bottom. To ensure the accuracy of my titrations I would test the concentrations of the standard solution I have made by either titrating it with an acid of known concentration or using short-range indicator paper. This would ensure my titration results were accurate. This should improve the accuracy of my results if I were to perform the experiment again. Josh Rowlands March 2002 2 ...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. Investigating the effects of varying pH levels on the germination of cress seeds

    Using the second of the remaining two 100cm�measuring cylinders I then measured 20cm� of the 1% concentrated solution which I added to the bottle and shook gently to mix the solution. After all the solutions had been made, I used Universal Indicator to measure the pH value of all the

  2. Vinegar. In this investigation I am going to find out the concentration of ethanoic ...

    The titration must be repeated until this is achieved. Burette readings must be recorded to 2 decimal places. Results table for a titration: Burette Rough 1st Accurate 2nd Accurate Final (cm�) Initial (cm�) Titre (cm�) Titre: final burette reading - initial burette reading We know that NaOH is in a

  1. How much Iron (II) in 100 grams of Spinach Oleracea?

    Moles = 0.0001565 mol dm-3 The ratio of Potassium Manganate (VII) (aq) to Iron (II) (aq) is 3:5 and therefore to work out the mols of Iron (II) used in the titration I need to divide the volume of moles by 3 and then multiply it by 5.

  2. Investigating the effects of changing the concentration of different solutions on the refractive index ...

    distance between the electrode (these two factors are held constant on the probe) * directly proportional to the concentration of the ions in the solutions, the more ions it contains, the higher the conductance. * directly on the mobility of the ions * directly on the temperature (this is held constant during the experiment)

  1. Determination of the equilibrium constant for esterification of ethanoic acid and propan-1-ol by using ...

    1.00 cm3 of the mixture was then transferred to the 100 cm3 conical flask prepared. 4. The initial burette reading was recorded. Then, the mixture in the conical flask was titrated with 0.4M NaOH until the end point is reached when the colour had changed from colourless to pink.

  2. Analyse the samples by titration and to decide which of the samples, if any ...

    Then fill the pipette to way past the line. 6. Carefully let the solution out until the meniscus is on the line. 7. I will then run the solution into a conical flask. 8. I will add 7 drops of indicator and the solution will turn purple and put it on the white tile that is on the clamp stand.

  1. Back Titration to find the Concentration of Vinegar (Ethanoic Acid)

    Again it will be green at the equivalence point at which the acid will be neutralised. * The first 2cm3 micropipette used for the base will be used to titrate the sodium hydroxide into each of the wells with ethanoic acid.

  2. Planning of Titration

    (This Titration will give you an idea of how to do the real experiment and any mistakes can be improved) * First rinse the Burette with distilled water to remove any dirt or other chemicals stuck in the burette. * Now rinse the burette with the acid to remove all the water in the burette.

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