 We're going to do an experiment to determine the equilibrium constant for the hydrolysis of an ester. We're going to react ethyl acetate with water to form acetic acid and ethanol. We will need to add some hydrochloric acid to the reaction mixture to act as a catalyst in order for the mixtures to reach equilibrium in a reasonable period of time. We'll make up a series of samples containing ethyl acetate, water, and hydrochloric acid. The first vial will contain only hydrochloric acid and will be used to determine the moles of HCl. We will put the same number of moles of HCl in each of the vials. The total volume in each of the vials will be held constant at 10 milliliters. After the reaction mixtures have reached equilibrium, we will titrate the contents of each of the vials using sodium hydroxide. The titration will allow us to determine the total number of moles of acid in each vial. Since the number of moles of HCl is constant in each of the vials, we will also be able to determine the moles of acetic acid in each vial. From the moles of acetic acid, we will be able to determine the moles of ethanol, the moles of ethyl acetate, and the moles of water in the reaction mixtures at equilibrium. This will allow us to determine the equilibrium constant for the reaction. In our first vial, we are going to pipette 5 milliliters of 3 molar HCl and 5 milliliters of water. 5 milliliters of 3 molar HCl and 5 milliliters of water. We will cap the vial tightly and vial 2 will pipette 5 milliliters of 3 molar HCl and 5 milliliters of ethyl acetate. We prepared 3 additional samples with varying amounts of 3 molar HCl, water, and ethyl acetate. The total volume of all the samples has been held constant at 10 milliliters. Over the period of a couple of days, we will swirl the vials to make sure that the solutions stay homogeneous. The reaction mixtures have now come to equilibrium and we are ready to titrate the solutions to determine the total number of moles of acid in the solution. We have both the moles of HCl, which were the catalyst, and the moles of acetic acid that were produced by the reaction. We are going to transfer the contents of the first vial to 125 milliliter flask. We are going to carefully rinse the vial with a little bit of water to make sure that we transfer all the reaction mixture to the flask. We are going to use phenethylene as our acid-base indicator, so we are going to add a few drops of phenethylene. The solution is acidic, so the solution is colorless at this point. We are going to titrate our samples until they turn a pale pink color. You will take initial burette reading as is normal in any type of titration. You will be able to read the burette to the nearest hundredth of a milliliter. We are going to slowly add the sodium hydroxide solution. The sodium hydroxide solution will react with both the HCl and the acetic acid. When we reach the pale pink end point, the number of moles the sodium hydroxide added will be equal to the total number of moles of HCl plus moles of acetic acid. With the titration, you should rinse down the walls of the flask to make sure that any material that is splattered on the sides of the flask gets a chance to react. When the solution is turned to pale pink color, you will take a final burette reading and you will calculate the total milliliters of any OH solution used for the titration. You will titrate the other four vials in a similar manner.