1. Chapter 13 Chemical Equilibrium

2. Reversible Reactions ___________ react to form products.
_________ then react to form reactants.
_____ reactions occur:
________
aA + bB  cC + dD
_______

3. CONCENTRATIONS __________ CHANGE!
EQUILIBRIUM OCCURS
When the amount of __________ becoming __________________ the amount of _________ becoming __________.
CONCENTRATIONS __________ CHANGE!
When the _________ and _________ reactions rates are ______.

4. EXAMPLE 2HI(g) ↔ H2(g) + I2(g) 2 HI react to form H2 and I2
As H2 and I2 build up, they react to form HI

5. EQUILIBRIUM EXPRESSION
If we compare the concentrations of all the reactants and products at equilibrium, we discover a relationship:
k = [ ]p
[ ]r
Can be many equilibrium concentrations possible for a given temp, ______________
Includes only _______ and ________, no pure solids or liquids
K and Keq and Kc can be substituted for each other.

6. 2HI(g) ↔ H2(g) + I2(g)
Write the equilibrium expression for this reaction.

7. N2(g) + H2(g)  NH3(g)
Write the equation and the equilibrium expression for the synthesis reaction between N2(g) and H2(g) to form NH3(g)
NOW….Write the equation and the equilibrium expression for the decomposition of NH 3(g)
WHAT DO YOU NOTICE ?
Inverse of each other

8. ANOTHER REACTION
Write the equation and the equilibrium expression for N2O4(g) decomposing into NO2 (g)
NOW write the equation and the equilibrium expression for 1/2N2O4 forming NO2(g)
WHAT DO YOU NOTICE ?

9. General rules K = [products]p [reactants]r
If you reverse the reaction, you _____the K
If you double the reaction, you _____the K
If you halve the reaction, you _____ the K

10. TRY THIS ONE ! Given this equilibrium expression: K = [SO2]2[O2]
Write the balanced equation.

11. Equilibrium Calculations
If you know the equilibrium concentrations of reactants & products, you can solve for K.
aA + bB  cC + dD
K = [C]c[D]d
[A]a[B]b

12. Sample Problem
When solid ammonium chloride is heated, it reaches equilibrium with ammonia and hydrogen chloride. It is found that at equilibrium at 500oC in a 5.0 L container, there is 2.0 mol NH3, 2.0 mole HCl, and 1.0 mol NH4Cl. Calculate K for this system.

13. GASES
Equilibrium problems can be done using the partial pressures of gases, and solving for Kp
Parenthesis are substituted for brackets.
See Example 13.4 in text

14. Kp and Kc A relationship exists between Kc and Kp. Kp= K(RT)Δn
R = L atm/mol K
T = temp in K
Dn = sum of the coefficients of the gas product minus sum of the coefficients of the gas reactants
Example 13.5

15. Homogeneous Equilibria
all reactant and products are in the ________
Heterogeneous Equilibria
Check out 13.6 later!

16. K allow us to predict several things about the reaction:3)

17. Tendency of a Reaction to Occur
If K>1, mostly _________ exist, equilibrium lies far to the ______
_________ Rxn is predominant
2. If K<1, mostly ________, equilibrium lies far to the _____

18. Reaction Quotient
Given some reactants AND some products together in a reaction vessel, which reaction ( or ) will occur to reach equilibrium.
Compare Q to K
K uses ____________ concentrations
Q uses ___________ concentrations

19. Q and K Sample Exercise 13.7 If K < Q, reaction shifts _______
If K = Q, reaction is __________

20. Calculate Equilibrium Concentrations
If given K & original concentrations, you can find equilibrium concentrations using an ICE chart

21. THE ICE CHART Reactant and Products are listed here!
Time for lots of examples and practice!
Reactant and Products are listed here!
I write my ICE chart underneath the balanced equation.
Initial
Change
Equilibrium

22. Le Chatelier’s Principle
When a chemical system is at equilibrium, and something changes- that change is a “_________”.
The equilibrium will adjust __________
_________________
It will move ________ or ________ to reduce the stress.
Common stresses are changing ________ _______________________________

23. Concentration
________ reactant or product, equilibrium _________________ the addition.
__________ reactant or product, equilibrium ___________ the subtraction
Try 13.13

24. Pressure Can be changed by 1) 2) 3)
Volume change directly related to moles
_______ volume, shift to ______ # of moles
Try 13.14

25. Temperature
Treat changes in temp ______________ _______________________
Treat heat like any other ________ or ___________.
Must know if rxn is ____________ or ___________
_________ heat, shift ________ the heat
__________ heat, shift _______the heat
Try 13.15

26. NOW WE PRACTICE A LOT!!!!