1. Day 6 Chemical Equilibrium
Lecture Presentation
Unit 7
Day 6 Chemical Equilibrium
James F. Kirby
Quinnipiac University
Hamden, CT
Edited by M. Day

2. Warm Up TAKE OUT: Lab Notebook and Lab Handout
MAKE NEW SECTION: Intro Activity Results
WORK TOGETHER: With Lab Partner to “Analyze the Results”
TIME: 12 MINUTES
WHEN DONE: Share which Lab Station you plan to start at (A, C, D, or E)

3. Agenda COMPLETE: All 4 Lab Stations
Homework: Explanation AND AP Review Questions
Use Background section of lab, class website, internet resources, and remind.com)

4. Lab Report: Procedure, Data, Discussion of Theory A
Lab Report: Procedure, Data, Discussion of Theory A. HIn (aq) ⇌ H+ (aq) + ln-(aq) H+(aq) + OH-(aq)  H2O(l)
Procedure
Observations
Explanation
Initial color of water and bromothymol blue
Add 0.1 M HCl
Add 0.1 M NaOH
Additional drops of HCl and NaOH

7. Lab Report: Procedure, Data, Discussion of Theory C
Lab Report: Procedure, Data, Discussion of Theory C. [Co(H2O)6]2+(aq) + 4HCl (aq) + Heat ⇌ [CoCl4]2-(aq) + 6H2O(l) Ag+(aq) + Cl-(aq)  AgCl(s)
Add Cobalt Complex Ion Color Information Somewhere on Procedure
Procedure
Observations
Explanation
Add 6.0 M HCl drops (tube A)
Add 0.1 M AgNO3 drops (tube B)
Add distilled water drops (tube C)
Add 5-6 grains CaCl2 to tube C
Test tube C placed in ice water bath for 2-3 minutes
Test tube C placed in hot bath for 2-3 mins

8. Lab Report: Procedure, Data, Discussion of Theory D
Lab Report: Procedure, Data, Discussion of Theory D. 2CO2 (g) + H2O (l) ⇌ CO2 (aq) + H+(aq) + HCO3-(aq)
Procedure
Observations
Explanation
Initial color of solution
Pull back on syringe to decrease pressure
Push syringe to increase pressure

9. Lab Report: Procedure, Data, Discussion of Theory E
Lab Report: Procedure, Data, Discussion of Theory E. Mg(OH)2 (s) ⇌ Mg2+(aq) + 2OH-(aq) H+(aq) + OH-(aq)  H2O (l)
Procedure
Observations
Explanation
Initial color of milk of magnesia and universal indicator
Add 1 drop of 3 M HCl with constant stirring
Additional drops of 3 M HCl
Additional drops of HCl and NaOH

10. Clean Up for the Next Group!

11. Applications of LeChatelier’s Principle
COMPLETE: All 4 lab stations WRITE: Observations (Explanation is homework) TIME: minutes per station WHEN DONE: CLEAN UP FOR NEXT GROUP

12. Lab Report: Procedure, Data, Discussion of Theory A
Lab Report: Procedure, Data, Discussion of Theory A. HIn (aq) ⇌ H+ (aq) + ln-(aq) H+(aq) + OH-(aq)  H2O(l)
Procedure
Observations
Explanation
Initial color of water and bromothymol blue
Solution is green
The green color shows that the pH of distilled water is between 6 and 7.6, and the indicator is a mix of Hln and I-
Add 0.1 M HCl
Solution turned yellow
pH < 6.0
Add 0.1 M NaOH
Solution turned green and finally ended on blue, pH > 7.6
Additional drops of HCl and NaOH
Solution changes from yellow (with HCl) to blue (with NaOH)

13. Lab Report: Procedure, Data, Discussion of Theory C
Lab Report: Procedure, Data, Discussion of Theory C. [Co(H2O)6]2+(aq) + 4HCl (aq) + Heat ⇌ [CoCl4]2-(aq) + 6H2O(l) Ag+(aq) + Cl-(aq)  AgCl(s)
Procedure
Observations
Explanation
Add 6.0 M HCl drops (tube A)
Solution turned blue
Add 0.1 M AgNO3 drops (tube B)
White solid precipitate and solution turned pink
Add distilled water drops (tube C)
Solution turned pink
Add 5-6 grains CaCl2 to tube C
Crystals dissolved and solution turned blue
Test tube C placed in ice water bath for 2-3 minutes
Test tube C placed in hot bath for 2-3 mins

14. Lab Report: Procedure, Data, Discussion of Theory D
Lab Report: Procedure, Data, Discussion of Theory D. 2CO2 (g) + H2O (l) ⇌ CO2 (aq) + H+(aq) + HCO3-(aq)
Procedure
Observations
Explanation
Initial color of solution
Green color = pH 4.4
Pull back on syringe to decrease pressure
Solution turned teal, pH = 4.8
Push syringe to increase pressure
Solution turned green, pH = 4.4

15. Lab Report: Procedure, Data, Discussion of Theory E
Lab Report: Procedure, Data, Discussion of Theory E. Mg(OH)2 (s) ⇌ Mg2+(aq) + 2OH-(aq) H+(aq) + OH-(aq)  H2O (l)
Procedure
Observations
Explanation
Initial color of milk of magnesia and universal indicator
Purple solution with white solid suspended in liquid
White solid is undissolved Mg(OH)2. Purple color is from the universal indicator and shows that some of the OH- ions are present b/c purple = pH > 10
Add 1 drop of 3 M HCl with constant stirring
Solution immediately turned pink with more stirring pink color turned orange, green, then blue
Additional drops of 3 M HCl
Solution immediately turned pink; slower change to the blue-green end color
Additional drops of HCl and NaOH
Solution immediately turned pink; color remained pink and solution not cloudy

16. Change in Reactant or Product Concentration
If the system is in equilibrium
adding a reaction component will result in some of it being used up.
removing a reaction component will result in some if it being produced.

17. Change in Volume or Pressure
When gases are involved in an equilibrium, a change in pressure or volume will affect equilibrium:
Higher volume or lower pressure favors the side of the equation with more moles (and vice-versa).

18. Change in Temperature
Is the reaction endothermic or exothermic as written? That matters!
Endothermic: Heats acts like a reactant; adding heat drives a reaction toward products.
Exothermic: Heat acts like a product; adding heat drives a reaction toward reactants.

19. An Endothermic Equilibrium

20. An Exothermic Equilibrium
The Haber Process for producing ammonia from the elements is exothermic.
One would think that cooling down the reactants would result in more product.
However, the activation energy for this reaction is high!
This is the one instance where a system in equilibrium can be affected by a catalyst!

21. Catalysts
Catalysts increase the rate of both the forward and reverse reactions.
Equilibrium is achieved faster, but the equilibrium composition remains unaltered.
Activation energy is lowered, allowing equilibrium to be established at lower temperatures.