Write a balanced equation for the following reaction: Ethyl ethanoate + water ethanol + ethanoic acid. 1a. 1b. 2. 3. 4. 1) Mass of empty tube / g. 12.01. 12.24. 12.57. 12.18. 12.73. 2) Add 2M HCl catalyst / cm 3. 5.0. 5.0. 5.0. 5.0. 5.0. 3) New mass / g. 17.03. 17.34.
Ethyl ethanoate + water ethanol + ethanoic acid
1) Mass of empty tube / g
2) Add 2M HCl catalyst / cm3
3) New mass / g
4) Add ethyl ethanoate / cm3
5) New mass / g
6) Add water / cm3
7) New mass / g
(shake occasionally during this time)
Titate the contents of each of the 5 tubes
For each tube, make sure all the contents have been emptied into the conical flask by flushing the tube out with distilled water.
Use phenolthalein indicator solution.
Table showing tube number and titre in cm3
Aim - Work out a value for Kc including any units.
Think carefully about the data you have and how you could use this to calculate Kc.
Discuss in groups – write your ideas down on a large sheet of paper, explaining your thought process.
5.0 cm3 HCl
4.0 cm3 ester
Kc = 0.0292 x 0.0292
0.012 x 0.3018
Kc = 0.24
Why can we calculate Kc using mol amounts not concentrations in this case?
In the titration section, what effect will using distilled water to wash out the test tube have?
Will using NaOH in the titration have any effect on the position of the equilibrium?
The burette had a published maximum error of +- 0.05cm3
Calculate the percentage error in the titre for tube 3.
The volumes all cancel.
Water is a reactant, increasing water will shift the equilibrium position to the right but will not effect Kc.
NaOH will remove some of the acid product. Removing product will shift the equilibrium position to the right. No effect on Kc
Percantage error = 2 x 0.05 x 100 = 0.255%
Titre would be higher as would take more NaOH to neutralise the acid. [ethanoic acid] would appear to be higher, Kc higher than it should be.
Forward reaction is exothermic, equilibrium position would move to the left to minimise the effect of the change. Kc lower than it should be.
No effect on Kc as it is only effected by temperature. Relative concentrations to not effect Kc.
A student read the pipette used for the acid and ester and read from the top of the meniscus, and did the same when reading from the burette containing NaOH
Effect on volume of acid?
Effect on volume of Naoh?
Volume of acid higher than it should be.
Volume of NaOH not effected because we measure by difference.