The Equilibrium Constant of an Ester Hydrolysis Reaction

Abstract: This experiment was conducted in order to discover the Kc, equilibrium constant, of a hydrolysis reaction of an unknown ester #2, unknown acid, and alcohol #2 products. The first week consisted of creating the reaction mixtures in bottles, next was preparing a NaOH solution while neutralizing with KHP. The final week consisted of titrating the bottles with the NaOH solution prepared previously. After calculations the Kc average was equivalent to 0.1031

Introduction: Chemical equilibrium in a reaction occurs when the rate of the forward reaction is equivalent to the rate of the reaction going backwards. Once a chemical reaction has attained equilibrium, the collisions are still continuing, it is just that the reaction is occurring the same in both directions at the same rate. Both the products and reactants are being formed in an equal amount of time. The concentration of both reactants and products are expressed by the equilibrium constant Kc.

Procedure: (Reference Lab Manual for Procedures)

Data:
The following table displays the reaction mixtures within the bottles Table 1.

Esther 2
Density: 0.8878 g/mL Molar Mass: 102.13 g/mol
Alcohol 2
Density: 0.7997 g/mL Molar Mass: 60.10 g/mol

Table 2 shows the NaOH solution standardized with the addition of KHP Table 2.

Table 3 is the titration of the reaction mixtures with the NaOH solution prepared. Table 3.

Calculations:
Standardize NaOH

Average NaOH after 3 trials was 0.6578 M NaOH

Moles of HCL

Molarity of HCL (average between bottle 1 & 1A)

Grams of HCL

Grams of Water
4.319g HCL = 4.7181 g H20
Moles of Water in HCL Solution

Moles of Water added

Moles of ester initially present moles of ester
Moles of alcohol initially present

Moles of acid present

Moles of carboxylic acid present, moles of alcohol formed, moles of ester disappeared, moles of water disappeared 0.0350 – 0.01185 = 0.0232

Average Kc = 0.1031
Table 4.

Table 5.

Discussion:
The results of the experiment, using Esther and Alcohol unknown number 2, gave a Kc value average equivalent to 0.1031.

Re5.