1. Announcements Exams will be handed back in lab next week.
Weekly quizzes for the rest of the semester.

2. The value of the equilibrium constant can be determined from concentration data

3. The reaction quotient is calculated from non-equilibrium concentrations to determine if a system is at equilibrium

4. How to solve equilibrium problems
Write the equilibrium expression
Determine Q
if Q = K, it’s at equilibrium
if Q < K, reactants go to form products
if Q > K, products go to form reactants
Call the amount reacting “x”
Solve for x in the equilibrium expression
Use x to determine equilibrium concentrations

5. Determining equilibrium concentrations when a system does not start at equilibrium
Given these initial concentrations, what will the final concentrations be when equilibrium is reached?
From last time: K=0.11, Q=7.25
Since Q>K, reaction goes in reverse to get to equilibrium
C2H5OH
CH3CO2H
CH3CO2C2H5
Initial
Change
Equilibrium

6. Equilibrium constants can also be written in terms of gas pressure
KP is not necessarily the same number as KC
2 NH3(g) N2(g) + 3 H2(g) Kc = 5.8 x 105
Kp =

7. An equilibrium will shift in response to change in the system or its environment
LeChatelier’s Principle

8. The effect of concentration changes on equilibria
Add product [C]
Remove reactant [A]
Remove all of reactant [B] and product [D]

9. The effect of volume changes on equilibria
Equilibrium will shift to side with fewer moles of gas

10. If we decrease the volume of this reaction, the equilibrium will…
Shift left
Shift right
Remain the same

11. The effect of temperature changes on equilibria
Endothermic reactions
Exothermic reactions

12. LeChatelier’s Principle- Quantitative
1-Liter flask contains 0.50 mol butane and 1.25 mol isobutane (at equilibrium). We then add 0.50 mol and butane. What happens and what are the final concentrations of isobutane and butane?