Equilibrator

You will meet some of these objective points in today's lesson:
4.5 c use practical data to establish the idea that a relationship exists between the equilibrium concentrations of reactants and products which produces the equilibrium constant for a particular reaction, eg data on the hydrogen-iodine equilibrium
4.5 d calculate a value for the equilibrium constant for a reaction based on data from experiment, eg the reaction of ethanol and ethanoic acid (this can be used as an example of the use of ICT to present and analyse data), the equilibrium Fe2+(aq) + Ag+ (aq) ⇌ Fe3+(aq) + Ag(s) or the distribution of ammonia or iodine between two immiscible solventsd calculate a value for the equilibrium constant for a reaction based on data from experiment, eg the reaction of ethanol and ethanoic acid (this can be used as an example of the use of ICT to present and analyse data), the equilibrium Fe2+(aq) + Ag+ (aq) ⇌ Fe3+(aq) + Ag(s) or the distribution of ammonia or iodine between two immiscible solvents
4.5 f demonstrate an understanding that when ∆Stotal increases the magnitude of the equilibrium constant increases since ∆S = RlnK
4.5 h relate the effect of a change in temperature on the value of ∆Stotal.
4.6 a demonstrate an understanding of how, if at all, and why a change in temperature, pressure or the presence of a catalyst affects the equilibrium constant and the equilibrium composition and recall the effects of changes of temperature and pressure on rate, eg the thermal decomposition of ammonium chloride, or the effect of temperature and pressure changes in the system 2NO2 ⇌ N2O4
4.6 d demonstrate an understanding of the importance of being able to control reactions, through knowledge of equilibrium constants and entropy changes, the importance of controlling reactions to produce adequate yields under safe, economically viable conditions and why some reactions ‘go’ and some will never occur.

Use the spreadsheet linked here to investigate equilibrium reactions

You can change three things:

1. Temperature (either Kelvin or Celsius)
   
2. The total pressure/volume of the system
   
3. The initial amount of each chemical, in moles
   

The spreadsheet automatically calculates:

1. The change in moles
   
2. The equilibrium moles and pressure
   
3. Initial reaction quotient
   
4. The final reaction quotient
   
5. Equilibrium constant
   
6. Gibb's free energy and ΔG
   

What to do!:
Change the three values stated above for each equilibria system, these are either typed in the white boxes or adjusted using the slider
Watch how your changes affect all of the spreadsheet calculated values
If the reaction quotient is larger than the equilibrium constant, what will happen?
Adjust the slider accordingly to reestablish equilibrium, this step must be done with conscious effort, you can learn a lot and get a very deep understanding of equilibria by observing the change in values as you adjust the slider. Simply playing with the slider with the mouse will be a waste of your time! :)
Change another value of the three choices above and repeat the process, make notes as you do so. Again adjust the slider to the equilibrium position after each change.

There are two graphs showing:
a) The initial and momentary pressures (or molarities)
b) The Gibbs free energy versus the extent of reaction, with the momentary value that corresponds to the slider position superimposed on this curve
Repeat the above steps and observe these graphs. Again move the equilibrium position slider with conscious effort.
What can you conclude from observation of these graphs?

Finding ideal conditions
In the systems shown, which value represents a good yield?
Change the values of temperature and pressure until you are obtaining a good yield.
Note down the conditions you would expect to be used for each reaction, do not give precise values. High temperature/Low pressure is good enough.
What other information would you need to know if you were to apply the information from the spreadsheet to design reaction conditions?