Its use in economics is imported from physics. In physics, it means a state of even balance in which opposing forces or tendencies neutralize each other.
The first thing that came to mind was a lab I modified that is centered around making connections between topics. Admittedly, this lab is not a "big idea" per se. So in this blog post, I would like to share a lab activity that relies on these connections - between stoichiometry, esterification, equilibrium, kinetics, titrations and uncertainty of calculations.
I will also share the resources I have created to support my students through the process of working through these calculations.
In terms of attribution, I will admit I created this lab modified from a number of sources see list below. I have modified it so much that it is difficult to know which source contributed which idea I borrowed. I offer my humble thanks to all of the sources used. I would suggest reading the lab handout at this point linked below.
The reaction used is an esterification reaction between ethanol and ethanoic acid. As mentioned earlier, I think students benefit from discussion of the connections between topics.
Depending on sequencing, this can be review of an esterification reaction already learned. It is also review of equilibrium calculations and how titration can be used to find equilibrium concentrations.
As for the pragmatics, the lab takes three days of class time. Day 1 is simply making the equilibrium mixture - and this typically takes minutes depending on the comfort level of my students with general lab practices.
The most efficient method of delivering the liquids I have found is setting up burettes around my lab with the required liquids.
I use multiple burettes of each liquid to prevent log jams. The students simply move from station to station collecting the required liquids - recording burette readings as they go. Day 2 is the titration.
I try to have at least two students with each mixture I have small classes so that their results can be compared. With a bigger class, this could be modified so that each group conducted one or more titrations - trying to give each student time on the burette for the experience.
The students also titrate the 3 M hydrochloric acid for their data processing. These two titrations typically take about an hour - plus or minus 15 minutes depending on the comfort level of the students with the process of titration - and whether you make the NaOH solution for them.
Day 3 involves going through the calculations. I typically start this at the end of Day 2 and ask students to put in their best effort before the following class, using the guideposts below: Guideposts For each mixture: Calculate the amount in mol of ethyl ethanoate, ethanoic acid, ethanol and water present in the original mixture i.
When calculating this for the water remember to take into account the water present in the dilute HCl. Using the titration information, calculate the amount in mol of ethanoic acid present in the equilibrium mixture and hence the amount in mol of ethanol, ethyl ethanoate and water in the equilibrium mixture.
Use ICE here after the titration calculation. Calculate the equilibrium concentrations of the water, ethyl ethanoate, ethanoic acid and ethanol in the mixture and hence the equilibrium constant.
Compare to the true value of 4.
The guideposts are not very detailed - and yet this series of calculations requires several steps that are linked together to come up with a final value for Kc.
Based on the difficulty - and my desire to guide students without doing all of the work for them - I created a detailed guide to the calculations that literally "talks" them through each step see the documents included in the Supporting Information at the bottom of the post.
My students commented that they could hear my voice as they read the directions. · The calculations involved in determining the equilibrium constant in this experiment become quite complex due to the use of aqueous solutions of ethanoic acid and hydrochloric acid in a system in which water is a participant [a spreadsheet would probably be very useful for the repetitive calculations,caninariojana.com There is, however, another method of determining the equilibrium constant, Keq, of a reaction.
Spectrophotometric analysis results in the quantitative determination of the oncentration of the product, through the Beer-Lambert's caninariojana.com://caninariojana.com Determination of the Equilibrium Constant of an Unknown Ester Hydrolysis Reaction Abstract The experiments to follow determined that the equilibrium concentrations of the reaction: ester + water alcohol + acid, are equal to moles of ester, moles of water, and moles each of alcohol and caninariojana.com://caninariojana.com · In order to determine the equilibrium constant, the stoichiometry of the chemical reaction must be known.
If the initial concentrations of all reaction species are known, the determination of the equilibrium concentration of acetic acid will permit you to calculate the equilibrium constant for this reaction. Note: Normally, as seen in caninariojana.com Lab/Exp Determination of an.
Determination of the Equilibrium Constant for Esterification Essay Sample. Esterification is the reaction of a carboxylic acid with an alcohol. This experiment is an esterification reaction between ethanoic acid and propanol when heated.
The equilibrium constant of esterification reactions have values ~1~10, which implies that considerable amounts of reactants exist in the equilibrium mixture. This problem is in practices surmounted by continuous removal all the product – especially water – from the reaction caninariojana.com?func=fulltext&aId=