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

Objective To find out the equilibrium constant, Kc, for the reaction below, using acid hydrolysis:

Extracts from this document...


Determining an Equilibrium Constant Objective To find out the equilibrium constant, Kc, for the reaction below, using acid hydrolysis: Principle Although the hydrolysis of ethyl ethanoate is very slow, by using dilute hydrochloric acid as catalyst, the above equilibrium can be attained in 48 hours. After 48 hours, the reaction mixture can then be titrated with standard sodium hydroxide solution. Finally, the equilibrium concentrations of four components below and hence, Kc of hydrolysis of CH3COOCH2CH3 can then be calculated: Chemicals 2M HCl, 1.0335M NaOH, ethyl ethanoate, phenolphthalein indicator Apparatus 5 small reagent bottles, 5ml pipette & filler, burette, measuring cylinder, conical flask, electronic balance, stand, white tile Procedure -- Preparation, allow reaching equilibrium position 1.> Label 5 reagent bottles & their stoppers as 1A, 1B, 2, 3 and 4. 2.> Weigh each reagent bottles with their stoppers and record their corresponding masses in Table 3. 3.> Pipette 2M HCl into each bottles, using measuring cylinders to transfer ethyl ethanoate into bottles 2,3,4 and water into bottles 3,4 according to the amount shown in Table 1. Table 1 shows the amount of chemicals added: Reagent bottle's number 1A 1B 2 3 4 Volume of HCl(aq) ...read more.


x 36.5 6.> Mass of water in HCl(aq) = mass of HCl(aq) added - mass of pure HCl = mass of HCl(aq) added - value obtained in (5) 7.> Initial amount of CH3COOCH2CH3(l) 8.> Equilibrium amount of CH3COOCH2CH3(l) = initial amount of CH3COOCH2CH3(l) - equilibrium amount of CH3COOH(l) = value obtained in (7) - value obtained in (3) 9.> Initial amount of H2O(l) 10.> Equilibrium amount of H2O(l) = initial amount of H2O(l) - equilibrium amount of CH3COOH(l) = value obtained in (9) - value obtained in (3) 11.> Equilibrium constant, Kc Table 3 summarizes all the data analysed: Reagent bottle's number 1A 1B 2 3 4 Mass of reagent bottle with stopper /g 101.01 69.99 67.71 62.52 66.57 (1) Amount of HCl /mol 0.01039 0.01039 0.01039 0.01039 0.01039 (2) Total amount of acid at eqm. /mol - - 0.03927 0.03597 0.02692 (3) Eqm. amount of CH3COOH(l) /mol - - 0.02888 0.02558 0.01653 (4) Eqm. amount of CH3CH2OH(l) /mol - - 0.02888 0.02558 0.01653 (5) Mass of pure HCl /g 0.3792 0.3792 0.3792 0.3792 0.3792 Mass of bottle after adding HCl(aq) /g 106.11 75.15 72.79 67.62 71.75 Mass of HCl(aq) ...read more.


Besides, the catalyst H+ does not affect the equilibrium position and the percentage yield, it only provides an alternative path with lower activation energies for both forward and backward reactions, thus speed up the time required for equilibrium to achieve. Since the amount of water formed is not much more than CH3COOCH2CH3, CH3COOH and CH3CH2OH, i.e. it's not constant and [H2O(l)] should be included in the equilibrium equation. The Kc obtained in this experiment has no unit since it's canceled out in 4 equilibrium expressions. The errors of Kc obtained may due to the hands touching the reagent bottles are wet, hence the mass of chemicals added seems to be a little bit more. This can be discovered in that the mass of HCl(aq) added to 5 reagent bottles are different (but they should be the same!) The Kc obtained in bottle 4 seems to be much larger than others. It may due to the prolong titrating the mixtures or the increase in [H2O(l)] promotes more CH3COOH(l) forming. Certainly, it may also due to the poor titration techniques. Conclusion Since Kc cannot be easily affected by physical factors, except for temperature. Hence, Kc of a certain reaction can be obtained by many methods, e.g. electrochemical method and colorimetrical method. The one used in this experiment is titrimetric one since the hydrolysis is kinetically slow. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Physical Chemistry section.

Found what you're looking for?

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

Here's what a teacher thought of this essay

5 star(s)

This is a very descriptive, well through out practical. It contains advanced mathematical analysis for an A2 course and draws good conclusions

This piece of work is 5 stars out of 5

Marked by teacher Brady Smith 23/05/2012

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 AS and A Level Physical Chemistry essays

  1. Determination of the Amounts of Sodium Hydroxide Solution and Sodium Carbonate in a Mixed ...

    /3 = 5.1 cm3 Number of moles of HCl in this step: 5.1/1000 X 0.09868 = 5.033 X10-4 mol.

  2. Analysis of Brick cleaner Aim: To find the percentage by mass of hydrochloric ...

    Discussion: The weight for the brick cleaner may not be 6.00g as the volumetric flask was not weighed again with the brick cleaner in it because that step was forgotten. So the result above was taken from another student that did the prac.

  1. Preparation of Standard solution and Standardization of Hydrochloric acid

    Moreover, the chemicals used which are chemically unstable may react with any other chemicals and lead to danger unexpectedly. Third, chemicals with low hygroscopicity and efflorescence are preferred to be used for preparing primary standard solution. The chemicals which show hygroscopic properties (e.g.

  2. Investigation to analyse some fruit and vegetable juices for the contents present in them.

    CHEMICALS REQUIRED - 1. Fehling's solution A 2. Fehling's solution B 3. Tollen's reagent (Ammoniacal AgNO3) 4. Benedict's solution 5. Iodine solution 6. Chloroform (CHCl3) 7. Concentrated nitric acid (HNO3) 8. Concentrated Sulphuric Acid (H2SO4) 9. Ethyl Alcohol (C2H5OH) 10.

  1. Law of conservation of matter lab report.The chemical reaction used to research is: ...

    Take the small square piece of paper and place it on the Analytical Balance. Tare the balance (set it to zero). Carefully weigh 1grams of Silver nitrate on it. 3. Now put the 1 grams of Silver nitrate into the graduated funnel of 100ml with 4ml of distilled water in it.

  2. How are standard solutions prepared & how is titration carried out in industry

    The end point is the precise of the result of which the reagents achieve equilibrium. You know when the end point has been reached when the reaction has been completed and it is shown by a colour change. The indicator is a very weak solution, which is able to show

  1. Compare the techniques and methods I used to measure the purity of a sample ...

    The bad points to this technique however were that it consumes too much time and in the meantime a lot of human-errors can occur. Also another bad point to this technique was that the results acquired are dependent on a lot of factors; such as the diluting substance you use and also the indicator you use.

  2. This investigation is an investigation to find the concentration of two unknown solutions, Na0H ...

    Aim The aim of this investigation is to find the unknown concentration of two solutions by titration. The first being Hydrochloric Acid (HCl) and the second being Sodium Hydroxide (NaOH). The investigation will also determine the volume need to neutralise the solution of either the acid or alkali.

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