Experimental Sciences

Measuring an Equilibrium Constant through Titration

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In order to understand how a system achieves equilibrium, we need to measure the concentration of reactants and products of a chemical reaction. To do this, IBDP Chemistry Grade 12 students used a common laboratory method known as Titration.

For this experiment, the following reversible chemical reaction was investigated:

Ethanol + Ethanoic Acid  Ethyl Ethanoate + Water

The picture shows the chemicals used for the experiment: Ethanol, Ethyl Ethanoate, Hydrochloric Acid and Water

The picture shows the chemicals used for the experiment: Ethanol, Ethyl Ethanoate, Hydrochloric Acid and Water

The picture above shows liquids being measured out from a burette.  The boiling tubes were stoppered as soon as the needed amounts of liquids were transferred into them.

The picture above shows liquids being measured out from a burette.  The boiling tubes were stoppered as soon as the needed amounts of liquids were transferred into them.

Student made sure to stopper all boiling tubes to prevent evaporation of the liquids inside

Student made sure to stopper all boiling tubes to prevent evaporation of the liquids inside

Through titration, it is possible to get the concentration of the reactants (ethanol, ethanoic acid) and products (ethyl ethanoate, water) by using an acid to catalyze the reaction. In the case of the experiment, a common acid, known as hydrochloric acid was used.

Student using NaOH as the titrant to measure the concentration of the liquids in the erlenmeyer flasks.

Student using NaOH as the titrant to measure the concentration of the liquids in the erlenmeyer flasks.

However, the reaction of ethanol and ethanoic acid, even with the aid of a catalyst was very slow.  It took the students approximately a whole week to finish the experiment.

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