Determination of the equilibrium constant for esterification

Esterification is the reaction of a carboxylic acid with an alcohol. This experiment is an esterification response between ethanoic acid and propan-1-ol when warmed: CH3COOH(aq) + CH3CH2CH2OH(aq) < CH3COOCH2CH2CH3(aq) + H2O(l) The development of propyl ethanoate is especially well-suited to the decision of the stability constant. The reaction is sluggish enough at room temperature level so the order of mixing, temperature level variations over the reaction time and even a last titration with a strong base just have little effect on the reaction.

Because this is a homogeneous reaction with the same number of moles of reactants and products, the stability continuous (Kc) is generally expressed in regards to molarity or can be computed in regards to moles alone which is more hassle-free. Since the reaction is extremely sluggish at room temperature level, it is accelerated by addition of driver (concentrated sulphuric(VI) acid ). But the catalyst does not take part in the overall response.

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The analysis of the equilibrium mixes is based on a simple titration with standardized NaOH.

Given that the preliminary quantities of all materials are understood and the overall changes in the response can be shown by the decision of the last amount of acid. The concentrated H2SO4 catalyst stays the same and when a quantity of acid is deducted out, there is only ethanoic acid. If less acid is discovered than initial addition, the response has moved in the forward instructions. If more acid is spotted, the response has actually relocated the reverse direction.

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Given that the stoichiometric ratios in the reaction are all unity, the loss or gain in ethanoic acid can be utilized to figure the loss or gain in whatever else.

Appropriate Equations/Chemical Reactions Involved: (1) Esterification reaction in between ethanoic acid and propan-1-ol: CH3COOH(aq) + CH3CH2CH2OH(aq) > CH3COONa(aq) + WATER(aq) 7. Chemicals: Glacial ethanoic acid 10. 5 g Propan-1-ol 10. 0 cm3 0. 50 M sodium hydroxide 50. 0 cm3 Concentrated sulphuric(VI) acid 8 drops Phenolphthalein sign 8.

Apparatus and equipment : Quickfit set 1 Safety spectacle 1 Burette 1 Wash bottle 1 Filter funnel 1 1. 0 cm3 pipette 1 White tile 1 Measuring cylinder 1.250 cm3 conical flask 2 Heat-proof mat 1 250 cm3 beaker 2 Anti-bumping granules Bunsen burner 1 Ice 9. Procedure : 1. 10. 5 g of glacial ethanoic acid and 10. 0 cm3 of propan-1-ol are put into a clean and dry peer-shaped flask. And then those were mixed thoroughly. 2. 1. 0 cm3 of the mixture was transferred by pipette to a 250 cm3 conical flask that about 25 cm3 of deionized water and 2 drops of phenolphthalein indicator were contained. The solution was then titrated to the end point with 0. 50 M sodium hydroxide solution. 3. The volume (V1 cm3) of titre was recorded.

8 drops of concentrated sulphuric(VI) acid were added to the remainder of the acid-alcohol solution and the flask was swirled continuously. 5. Step 2 was repeated immediately. 6. The volume (V2 cm3) of titre was recorded. 7. A few anti-bumping granules were added to the flask and then it was attached to a water-cooled reflux condenser. 8. The solution was refluxed for 30 minutes. Then, the flask was cooled by an ice bath. 9. Step 2 was repeated again. 10. The volume (V3 cm3) of titre was recorded. 11. The solution was refluxed continuously for additional 20 minutes.

Then, the flask was also cooled by an ice bath. 12. Step 2 was repeated again. 13. The volume (V4 cm3) of titre was recorded. 10. Observations : The reaction mixture changed from colourless to red in titration. 11. Data, Calculation and Results : Titration 1 2 3 4 Final burette reading (cm3) 22. 00 41. 50 6. 55 12. 00 Initial burette reading (cm3) 2. 90 22. 00 0. 85 6. 55 Volume of titre (cm3) 19. 10 19. 50 5. 70 5. 45 V1 = 19. 10 cm3 V2 = 19. 50 cm3 V3 = 5. 70 cm3 V4 = 5. 45 cm3 Volume of sodium hydroxide required for neutralizing concentrated sulphuric(VI) acid = V2 – V1 = 19. 5 – 19.

1 = 0. 40 cm3 Volume of sodium hydroxide required for neutralizing remained ethanoic acid after refluxing for 30 minutes = V3 – (V2 – V1) = 5. 70 – 0. 40 = 5. 30 cm3 Volume of sodium hydroxide required for neutralizing remained ethanoic acid after refluxing for 50 minutes = V4 – (V2 – V1) = 5. 45 – 0. 40 = 5. 05 cm3 12. Conclusion : The equilibrium constant of esterification was found to be 7. 74. 13. Discussion : 1. Small amount of concentrated sulphuric(VI) acid was added to the reaction mixture at the beginning of the experiment as a catalyst in order to speed up the reaction.

Anti-bumping granules should be added to the reaction mixture before refluxing so as to prevent super-heating. It can ensure smooth boiling. 3. The refluxing should be continued in step (11) until the titre of sodium hydroxide used approaching constantso as to ensure equilibrium is reached. 4. Equation for the esterification reaction between ethanoic acid and propan-1-ol: CH3COOH(aq) + CH3CH2CH2OH(aq) <=> CH3COOCH2CH2CH3(aq) + H2O(l) 5. No. of moles of ethanoic acid = no. of moles of sodium hydroxide used = 0. 5 x 5. 05 x 10-3 = 2. 525x 10-3 mol.

Concentration of ethanoic acid remaining at the end of the reflux = 2. 525x 10-3 / (1 x 10-3) = 2. 525 M 6. Concentration of propan-1-ol = Concentration of ethanoic acid = 2. 525 M Concentration of propyl ethanoate = 0. 5 x (V2 – V4) / (1 x 10-3) = 0. 5 x [(19. 5 – 5. 45) x 10-3] / (1 x 10-3) = 7. 025 M Concentration of water = Concentration of propyl ethanoate = 7. 025 M 7. Kc = [CH3COOCH2CH2CH3(aq)] [ H2O(l) ] [CH3COOH (aq)][ CH3CH2CH2OH (aq)] 8. Kc = (7. 025/2. 525)2 = 7. 74

If the concentration of the sodium hydroxide solution is not known exactly, it would not have any effect on the determination of the equilibrium constant for the esterification reaction. Since Kc = [CH3COOCH2CH2CH3(aq)] [ H2O(l) ] [CH3COOH (aq)][ CH3CH2CH2OH (aq)] Kc = { [NaOH]( V2- V4 ) / [NaOH] [V4 – (V2 – V1)]}2 = { ( V2- V4 ) / [V4 – (V2 – V1)] }2 Thus, Kc is not affected by the concentration of sodium hydroxide.

There is error in this experiment. (1) Taking reading in titration. Error estimation – When taking initial reading, error is + 0. 05 cm3. When taking final reading, error is also + 0. 05 cm3. Therefore, error is + 0. 1 cm3.

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Determination of the equilibrium constant for esterification. (2017, Aug 10). Retrieved from https://studymoose.com/determination-of-the-equilibrium-constant-for-esterification-essay

Determination of the equilibrium constant for esterification

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