WELCOME BACK!!
TODAY’S NOTES 3/31/14
Le Chatelier’s Principle
Systems at equilibrium
-once something is at equilibrium you can nudge it to get it out of equilibrium
Does not like that
Textbook definition: --When a change/stress (in concentration, temperature, pressure, volume, addition of catalyst…) is applied to a system that is already at equilibrium, the position of equilibrium SHIFTS in a direction that tends to reduce the effect of that change
i.e.: -If a system is at equilibrium and you add reactants, it will shift to make more products until it reaches equilibrium again
i.e.: -If you add more heat, it will shift back to the place when it has less heat
3 Delta’s to think about:
1. Concentration
2. Pressure and volume
3. Temperature
1. Delta (change) in concentration
- When a reactant/product is added to a system that is at equilibrium, the system shifts away from the added component
- If a reactant or product is removed, the system shifts towards the removed component
- i.e. A(aq) + B(aq) → C(aq) + D(aq)
- add more A and the system shifts right to remove extra A
*Aqueous and gas rule applies
2. Delta (change) in pressure/volume
- Gas Laws:
- As volume goes down, pressure goes up (keeping temp constant)
- As volume goes up, pressure goes down (keeping temp constant)
- Systems that involve gases
- i.e.: 2A(g) + B(g) → 3C(g) + D(g)
- (3 moles reactants & 4 moles products)
- pressure increases, system shifts to the side with fewer molecules/moles of gas
- pressure decreases, system shifts to the side with more molecules
*Change of volume is “code” for change in pressure
3. Delta (change) in temperature
- Reminder: The value of k does change with temperature!
- Exothermic reaction: A(g) + B(g) → 3D(g) + heat
- As temp goes up, reaction shifts left (to try to get rid of extra heat energy)
- Endothermic: heat + A(g) + B(g) → 3D(g)
- As temp goes down, reaction shifts right
*Shifts away from thing that is making stress
Look at 4 HANDOUTS
-Intro to LeChatelier’s Principle
-LeChatelier’s Principle 1
-LeChatelier’s Principle 1 (cont)
-LeChatelier’s Principle 2
FINISHED 1st 2 worksheets in class (completed copies in notes folder)
HOMEWORK:
-Webassign due tomorrow at 11:59 pm
Finish worksheets:
-LeChatelier’s Principle 1 (cont)
-LeChatelier’s Principle 2
The next scribe: KATE MAKI
