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Esterification Equilibrium

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Introduction

IB Group 4 Internal Assessment Chemistry Biology Physics Name: Date(s): Candidate Number: Session: Level: Investigation Title: Internal Assessment Marking Form Criterion Required Aspects Level Complete (2) Partial (1) Not at All (0) Data Collection and Processing Records appropriate quantitative and associated qualitative raw data, including units and uncertainties where relevant. Records appropriate quantitative and associated qualitative raw data, but with some mistakes or omissions. Does not record any appropriate quantitative raw data or raw data is incomprehensible. 2 1 0 Aspect 1 - Recording Raw Data Aspect 2 - Processing Raw Data Processes the quantitative raw data correctly. Processes quantitative raw data, but with some mistakes and / or omissions. No processing of quantitative raw data is carried out or major mistakes are made in processing. 2 1 0 Aspect 3 - Presenting Raw Data Presents processed data appropriately and, where relevant, includes errors and uncertainties. Presents processed data appropriately, but with some mistakes and / or omissions. Presents processed data inappropriately or incomprehensibly. 2 1 0 Conclusion and Evaluation States a conclusion, with justification, based on a reasonable interpretation of the data. States a conclusion based on a reasonable interpretation of the data. States no conclusion or the conclusion is based on an unreasonable interpretation of the data. 2 1 0 Aspect 1 - Concluding Aspect 2 - Evaluating Procedure(s) Evaluates weaknesses and limitations. Identifies some weaknesses and limitations, but the evaluation is weak or missing. Identifies irrelevant weaknesses and limitations. 2 1 0 Aspect 3 - Improving the Investigation Suggests realistic improvements in respect of identified weaknesses and limitations. Suggests only superficial improvements. Suggests unrealistic improvements. 2 1 0 Introduction: The equilibrium constant could be calculated by using the formula. Where A + B -> C + D In determining the equilibrium constant for an esterification reaction, The equilibrium constant, KC , would be; The research question would be; determine the KC values for different mixtures. ...read more.

Middle

Mixture 1 contains 5ml of HCl and 5ml of ethyl ethanoate. There is no water present in this mixture; however, since HCl is in aqueous state, there is water present in the HCl solution. NaOH + HCl HCl -> H+ + Cl- C 0.9531M 3.2M => V 33.24x10-3 0.01 n 0.032 mols 0.032 mols 0.032 mols 0.032 mols 0.032 mols Hence, the amount of pure HCl could be calculated; Since there were 5ml of HCl solution in the mixture, then the amount of water could be calculated; Mixture 1 contained 5ml of ethyl ethanoate. To find the number of moles for ethyl ethanoate in equilibrium; NaOH + HX C 0.9531 V 44.65 n 0.043mol 33.24x10-3dm3 of NaOH was needed to react with 10ml of HCl, since in mixture 1 has 5ml of HCl, amount used of NaOH to react with HCl needs to be taken off from the overall amount of NaOH used for the mixture. Uncertainty Calculations Uncertainty = (0.9531�0) x (44.65x10-3�1.5x10-4) = 0.043�0.0034 Uncertainty Calculations Uncertainty = (44.65x10-3�1.5x10-4) - [(33.24x10-3�1.5x10-4)/2] = (44.65x10-3�1.5x10-4) - (16.62x10-3�7.5x10-5) = 28.03x10-3�2.25x10-4 NaOH + HX C 0.9531 3.20 V 28.03 x 10-3 0.005 n 0.027mol 0.027mol Number of mols of ethanoic acid in equilibrium would be 0.027mol. Since initial is 0 mols and equilibrium is 0.027, the change is 0.027 mols. Moving onto water, as shown above, there is no water present in the mixture, but only in the HCl, which is 3.83ml. If 3.83ml is to be converted into moles, then the number of moles at initial state would be; Uncertainty Calculations Uncertainty = (0.9531�0)x(28.03x10-3�2.25x10-4) = 0.0027�2.17x10-5 Because the change is 0.0027�2.17x10-5 mols, the number of moles of water in equilibrium is; 0.212�0.0009mol - 0.0027�2.17x10-5 = 0.185�9.217x10-4 As the initial number of moles of ethyl ethanoate in equilibrium could be calculated; Because the change is 0.027mols, the number of moles of ethyl ethanoate in equilibrium is; 0.052�2.286x10-4 - 0.027�2.17x10-5 = 0.025�2.50x10-4 mols. ...read more.

Conclusion

Improvements: Table 11. Lists of Improvements Experiments Effects Improvements Overshooting the end point By overshooting NaOH to the flask, the end point will be affected Calculate the end point of the titration and then perform titration, or carry out a rough titration and then perform a proper titration afterwards Subjectivity of the colour change Different people have different views on colour change Allow only one person to state whether if there was colour change or not. Also, to help the clear view of the colour change, place a blank white page behind the flask Use of different burettes to make the mixture By using different burettes to make the mixture, the uncertainty of the equipment will pile up Since there is no way of not using separate equipments to make the mixture, equipments with smaller uncertainty increments could be used Number of trials performed Due to lack of time, there was only one trial been performed Extend the number of trials and by cutting out the outliers, the uncertainty of each titrations Concentration of NaOH NaOH was made by the lab technicians. Therefore uncertainty of the concentration will exist, however, there was no mention about the uncertainty of NaOH Ask the lab technicians about the uncertainty of the NaOH Refilling the burette Some of the titrations for the mixtures exceeded 50mls; hence the burette had to be refilled. Due to this, the uncertainty doubled. Use a burette that can contain more than 50ml of the solution The time allowed to reach the equilibrium The mixture was left for one week in room temperature for it to reach equilibrium. Since it takes one week roughly, hence some of the mixture may not have reached equilibrium. Leave the mixture for around two weeks in room temperature for it to fully reach equilibrium Possibility of the equilibrium to shift during the titration due to room temperature The room temperature has to be set in 298K. However, due to air conditioner, the room temperature may have changed. ...read more.

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