1. Equilibrium
Unit 6 Chemistry Spring 15

2. Agenda 5/1
Equilibrium Game
Happy Prom Weekend!!

3. Equilibrium Game A  B Reaction Cylinder A Cylinder B
One straw
Cylinder B
Other straw
Equilibrium is reached when volume in each tube is no longer changing during transfers

4. Agenda 5/4/15 Warm-Up Equilibrium Game conclusion Questions
Notes: Intro to Equilibrium
Conclusion: Equilibrium Game
HW: None

5. May the 4th be with you

6. Stoich Review
If a reaction requires 10.0g of bromine gas at STP, how many liters of bromine would this reaction use?

7. Equilibrium What is equilibrium? Equilibrium Game
1. Level of water in each cylinder stays CONSTANT
2. Rate of water transfer to A = Rate of water transfer to B
*EQUAL RATES of transfer between reactants and products*
NOT equal amounts!!

8. Equilibrium 2. Opposite processes at equal rates Reactants  Products
Characteristics of Equilibrium
1. Constant property
vapor pressure
concentration of soln
levels of H2O
Colors
2. Opposite processes at equal rates
Reactants  Products

9. Equilibrium Requirements to Maintain Equilibrium
1. Reversible process or reaction ()
2. Closed system - nothing added or removed (not necessarily sealed except for gases)
3. Constant T

10. Equilibrium Altering Equilibrium “stress” or change occurs
Equilibrium Game A B
1. Alteration or change -- also called disturbance or stress
How did adding more H2O change the amount of B?

11. Equilibrium 2. Effect on Equilibrium System
a) system reacted by increasing amount of H2O in B (right side, products)
b) new equilibrium was achieved sooner
now more water in A and B
some of added water was transferred to B, but not all of it

12. Agenda 5/05/15 Collect: Equilibrium Conclusion Le Chatlier’s Lab
Notes: Le Chat’s Principle
HW: Complete Lab Write Up

13. Revenge of the Fifth

14. Warm- UP
What is the pressure in atm of a .200 mol of gas that has a volume of 2.5L and is at 23 degrees celsius?

15. Agenda 5/6/15 Warm-Up Hand Back Equilibrium Tests Conclude Le Chat Lab
Collect
Notes: Le Chat’s Principle

16. Warm-Up
If you have a solution that contains 15.0g of NaCl in 125mL of water, what is the molarity of the solution?

17. Le Chatlier’s Principle
What is Le Chat’s Principle and how can it be used to determine the changes in an equilibrium?

18. Equilibrium LeChatelier’s Principle
If an equilibrium is subjected to a stress, the equilibrium is shifted in the direction that relieves the stress

19. Equilibrium Post Lab - Disturbing the Equil. Expt. 1. Concentration
a. Increase conc. on one side of eqn.
-- shift to opposite side of eqn.
b. Decrease conc. Or removal due to reaction w/ a substance on one side of the eqn.
-- shift to same side of eqn.

20. Equilibrium 2. Temp Change (heating/cooling)
a. Increase heat on one side
-- shift to opposite side
b. Decrease heat on one side
-- shift to same side

21. Equilibrium What happens: Equilibrium means the reaction is HAPPY! :D
Increased reactants cause forward rate to be faster (Products get jealous)
More products are formed (to make up for jealousy)
Eventually -- rates equal out -- new equilibrium
HAPPY AGAIN!!

22. Equilibrium What happens:
Decreased reactants cause forward rate to slow down (Reactants get jealous)
More reactants are formed (to make up for jealousy)
Eventually -- rates equal out -- new equilibrium
HAPPY AGAIN!!

23. Equilibrium Key: ____ stress, change, alteration, disturbance
____ increase in concentration or heat
____ decrease in concentration or heat (also removal or reaction of substance removing it)
____ shift to right side of equation
____ shift to left side of equation s

24. Equilibrium Stress Equilibrium Shift Examples: Cu (s) + 2Ag+ (aq)
Cu2+ (aq)
+ 2Ag (s)
Ag+ s
Add Cl-
Ag+ + Cl- s
AgCl
Rxn
removes
Ag+

25. Equilibrium Example 2: Stress N2O4 (g) + Heat 2NO2 (g) Heat
(increase T) s
Cool
(Remove heat) s

26. Agenda 5/7/15 Warm-Up Notes: Le Chat Notes: Equilibrium Constants
Thermodynamics
Notes: Le Chat
More Practice Problems
Notes: Equilibrium Constants
Practice Writing and Using K Expressions
TEST MONDAY

27. Warm-Up
A 2.0 g sample of water is heated. Its temperature is changed by 86 degrees Celsius. How much heat was gained by the water?

28. Equilibrium Effects on a Gas at Equilibrium
2 H2 (g) + O2 (g) < 2 H2O(g)
Decreasing volume (increasing pressure)
Cause a shift to the side that takes up less space
Increase volume (decrease pressure)
Cause a shift toward side that takes up more space

29. Increase in volume is like…

30. Equilibrium Stress Reddish- brown N2O4 (g) + Heat 2NO2 (g) colorless
System wants to decrease pressure
Increasing P by decreasing V
by forming less molecules
System wants to increase pressure
Decreasing P by increasing V
by forming more molecules

31. *Remember - P and V of gases are inversely proportional!*
Equilibrium
Strategy for gases:
Count the total # of gaseous molecules on each side (remember: s, l, aq not changed by P)
Increased V means more room for gas. The system uses this room. (Decrease in P)
Decreased V means less room for gas. The system makes up for this. (Increased P)
If stress is listed as increased or decreased P, reinterpret as change in V and solve as listed in #1-3.
*Remember - P and V of gases are inversely proportional!*

32. Equilibrium Effect of Catalyst on Equilibrium
Catalyst increases rate of reaction
Increases BOTH forward and reverse reactions
Net effect: no shift -- no changes in concentration
Reaches equilibrium faster

33. Equilibrium Expressions
How can you write an equilibrium expression and how can you use it to determine a shift in equilibrium?

34. Quantitative Aspects of Equilibrium
Equilibrium Constant Expression
Definition - mathematical expression of concentrations of products and reactants that results in a constant ratio

35. Quantitative Aspects of Equilibrium
The General Form:
Keq = [products]
[reactants]
Example:
N2 (g) + 3H2 (g) 2NH3 (g)
Keq = [NH3]2
[N2][H2]3

36. Quantitative Aspects of Equilibrium
Rules for Writing Equil. Constant Expression Equations
Each product on top in a []
Each reactant on bottom in a []
Coefficients from chemical equation become exponents on the [] in the equil. equation
Concentration of liquids and solids are NOT included in the equil. eqn.
-- leave out (s) and (l)

37. Quantitative Aspects of Equilibrium
Examples:
N2 (g) + 3H2 (g) NH3 (g)
Keq = [NH3]2
[N2][H2]3

38. Quantitative Aspects of Equilibrium
PbCl2(s) Pb2+(aq) + 2Cl-(aq)
Keq = [Pb2+][Cl-]2
HCl(g) + H2O(l) H3O+(aq) + Cl-(aq)
Keq = [H3O+][Cl-]
[HCl]

39. Quantitative Aspects of Equilibrium
Simple Calculations using Equilibrium Constant Expression Equations
See Handout…

40. Quantitative Aspects of Equilibrium
Significance of the Magnitude (Size) of the Values for the Equilibrium Constant
Keq = [products]
[reactants]
If Keq > 1: Products of the reaction are favored
If Keq < 1: Reactants of the reaction are favored

41. Quantitative Aspects of Equilibrium
Examples:
Large equil constant -- greater than 1.0
A B Keq = 120
Keq = [B]
[A]
Ratio: 120 = [B]
[A]

42. Quantitative Aspects of Equilibrium
2. Small equil constant -- less than 1.0
C D Keq = 2.5x10-10
Keq = [D]
[C]
Ratio: 2.5x10-10 = [D]
[C]