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Marg's Equilibrium Lab Procedures
Notes:
Definition: If you apply a stress to an equilibrium problem, the system will try to get rid of that stress in order to go back to the original equilibrium.
Mr. McLeod addition to definition:
a. System can only make more reactant (run the backward reaction) or more product (run the forward reaction), nothing else.
b. System will never get back to original equilibrium (since you add something in that has matter and energy) but comes to a new equilibrium. This is what the shift means, compare the original equilibrium material (ratio of reactant to product) compared to the new equilibrium material (ratio of reactant to product)
How you answer LeChatlier's Principle problems for Mr. McLeod (see blank answer form below)
1. What is stress
2. When you are reducing stress, do you make more reactant or product (for pressure you need to indicate # of total reactant particles and product particles)
3. Favors the forward or backward reaction (for change in temp must add endo or exo)
4. Shift equil to the Right or Left.
a. Shift equilibrium to the Left means that the new equilibrium position has a higher ratio of reactants to product than in the original equilibrium position.
b. Shift equilibrium to the Right means that the new equilibrium position has a higher ratio of product to reactant than in the original equilibrium.
For AP students (how actual amount of material change or is it actual concentrations of reactant to product or the ratio of reactant to product for original to new equilibrium position??):
Here is a blank answer form you will fill out for each LeChatelier's Principle problem.
Stress: _______________________________________________________________
How rxn tries to remove stress: _________________________________________________
Circle: Make more product or more reactant (fill in for pressure changes)__________________
Circle: Favoring: Forward rxn or Backward rxn: (fill in for temperature changes) _____________
Circle: Shift Equilibrium to: Left(more reactant) or Right (more product)
Solubility Equilibria
Write reversible reaction here.
Stress: Add 12 M HCl____________________________________________________
How rxn tries to remove stress: _________________________________________________
Circle: Make more product or more reactant (fill in for pressure changes)__________________
Circle: Favoring: Forward rxn or Backward rxn: (fill in for temperature changes) _____________
Circle: Shift Equilibrium to: Left(more reactant) or Right (more product)
Lab observation and reason: ___________________________________________________
Stress: Add 1.0M HCl_______________________________________
How rxn tries to remove stress: _________________________________________________
Circle: Make more product or more reactant (fill in for pressure changes)__________________
Circle: Favoring: Forward rxn or Backward rxn: (fill in for temperature changes) _____________
Circle: Shift Equilibrium to: Left(more reactant) or Right (more product)
Lab observation and reason: ___________________________________________________
Complex Ion Equilibria #1
Write the reversible reaction for this section (include colors)
Test tube 1 is control (so only has created solution in it: No stress
Test tube __2____
Stress: _______________________________________________________________
How rxn tries to remove stress: _________________________________________________
Circle: Make more product or more reactant
Circle: Favoring: Forward rxn or Backward rxn
Circle: Shift Equilibrium to: Left(more reactant) or Right (more product)
Solution turned: More Light Brown or More Red or No change
Compare to lab observation: __________________________________________
Test tube ___3___
Stress: _______________________________________________________________
How rxn tries to remove stress: _________________________________________________
Circle: Make more product or more reactant
Circle: Favoring: Forward rxn or Backward rxn
Circle: Shift Equilibrium to: Left(more reactant) or Right (more product)
Solution turned: More Light Brown or More Red or No change
Compare to lab observation: __________________________________________
Test tube ___4___
Stress: _______________________________________________________________
How rxn tries to remove stress: _________________________________________________
Circle: Make more product or more reactant
Circle: Favoring: Forward rxn or Backward rxn
Circle: Shift Equilibrium to: Left(more reactant) or Right (more product)
Solution turned: More Light Brown or More Red or No change
Compare to lab observation: __________________________________________
Complex Ion Equilibria #2
Write reversible reaction here:
For this reaction you need to know a few more pieces of information.
1)HCl --> H+ (or H3O+) + Cl1-
So, in a bucket of HCl solution, there is no HCl but only H+ and Cl1- ions.
Therefore, adding HCl really means adding H+ (or H3O+)
2) NaOH ---> Na1+ + OH1-
Then the OH1- + H+ ---> H2O
Looking at the above two equation, one needs to realize that you can explain lab observations in two different ways with respect to LeChatlier's Principle.
2a) OH1- from the NaOH consumes H+ as in the above reaction so adding the chemical is actually a decrease in [H+] or
2b)OH1- from the NaOH reacts with H+ to form H2O so adding the chemical is actually increase [H2O].
So, for the reactions with NaOH below, please alternate explanation (once using 2a & another times using 2b).
Test tube ___5 (HCl added)___
Stress: _______________________________________________________________
How rxn tries to remove stress: _________________________________________________
Circle: Make more product or more reactant
Circle: Favoring: Forward rxn or Backward rxn
Circle: Shift Equilibrium to: Left(more reactant) or Right (more product)
Solution turned: More Yellow or More Orange or No change
Compare to lab observation: __________________________________________
Test tube _6 (HCl added)_____
Stress: _______________________________________________________________
How rxn tries to remove stress: _________________________________________________
Circle: Make more product or more reactant
Circle: Favoring: Forward rxn or Backward rxn
Circle: Shift Equilibrium to: Left(more reactant) or Right (more product)
Solution turned: More Yellow or More Orange or No change
Compare to lab observation: __________________________________________
Test tube ___6 (NaOH added)___
Stress: _______________________________________________________________
How rxn tries to remove stress: _________________________________________________
Circle: Make more product or more reactant
Circle: Favoring: Forward rxn or Backward rxn
Circle: Shift Equilibrium to: Left(more reactant) or Right (more product)
Solution turned: More Yellow or More Orange or No change
Compare to lab observation: __________________________________________
Test tube __7 (NaOH added)____
Stress: _______________________________________________________________
How rxn tries to remove stress: _________________________________________________
Circle: Make more product or more reactant
Circle: Favoring: Forward rxn or Backward rxn
Circle: Shift Equilibrium to: Left(more reactant) or Right (more product)
Solution turned: More Yellow or More Orange or No change
Compare to lab observation: __________________________________________
Test tube __8 (NaOH added)____
Stress: _______________________________________________________________
How rxn tries to remove stress: _________________________________________________
Circle: Make more product or more reactant
Circle: Favoring: Forward rxn or Backward rxn
Circle: Shift Equilibrium to: Left(more reactant) or Right (more product)
Solution turned: More Yellow or More Orange or No change
Compare to lab observation: __________________________________________
Test tube __8 (HCl added)_____
Stress: _______________________________________________________________
How rxn tries to remove stress: _________________________________________________
Circle: Make more product or more reactant
Circle: Favoring: Forward rxn or Backward rxn
Circle: Shift Equilibrium to: Left(more reactant) or Right (more product)
Solution turned: More Yellow or More Orange or No change
Compare to lab observation: __________________________________________
Acid Base Equilibria
Write reversible reaction here:
Test tube 1 is control (so only has created solution in it: No stress
Test tube __2____
Stress: _______________________________________________________________
How rxn tries to remove stress: _________________________________________________
Circle: Make more product or more reactant
Circle: Favoring: Forward rxn or Backward rxn
Circle: Shift Equilibrium to: Left(more reactant) or Right (more product)
Solution turned: More Light Brown or More Red or No change
Compare to lab observation: __________________________________________
Test tube ___3___
Stress: _______________________________________________________________
How rxn tries to remove stress: _________________________________________________
Circle: Make more product or more reactant
Circle: Favoring: Forward rxn or Backward rxn
Circle: Shift Equilibrium to: Left(more reactant) or Right (more product)
Solution turned: More Light Brown or More Red or No change
Compare to lab observation: __________________________________________
Test tube ___4___
Stress: _______________________________________________________________
How rxn tries to remove stress: _________________________________________________
Circle: Make more product or more reactant
Circle: Favoring: Forward rxn or Backward rxn
Circle: Shift Equilibrium to: Left(more reactant) or Right (more product)
Solution turned: More Light Brown or More Red or No change
Compare to lab observation: __________________________________________