1. The Interaction of Energy and Matter
Chm 3.1

2. Collision Theory Molecules must collide to react
Collision energy must reach Ea
Molecules must be oriented correctly

3. Reaction Rates (Kinetics)
Reaction – bonds broken and reformed
Rate of Reaction is a result of collisions
#of effective collisions

4. Equilibrium for Chemical Reactions
Reactions can be reversible
Equilibrium = rate for forward reaction equals the rate of the reverse.
Concentrations of reactants and products remain unchanged
Watch

5. Equilibrium Expressions
nA + mB  xC + yD
K = the equilibrium constant
- a ratio of products to reactants at equilibrium
[C]x[D]y
[A]n[B]m
K =

6. H2 (g) I2 (g)  HI (g)
Write the equilibrium expression for the above reversible reaction.

7. What K means? When K is large, (K>1) When K is small, (K<1)
more products than reactants
EQ lies to the right
When K is small, (K<1)
more reactants than products
EQ lies to the left

8. Stresses on Systems at Equilibrium
Le Châtelier’s Principle:
Any stress applied to a system at EQ
The system will respond to minimize that shift
Stresses (changing)
Pressure
Temperature
Concentration

9. Changes to Pressure When pressure of system is changed
Pressure Increased
Reaction will shift toward side with least moles of gas
Pressure Decreased
Reaction will shift toward side with more moles of gas

10. Changes to Concentration
Increasing concentration = increasing amount
Reaction will shift to consume the excess
Decreasing concentration = decreasing amount
Reaction will shift to produce more

11. Changes in Temperature
Increasing the temperature will cause the reaction to shift to whichever side consumes the energy
Endothermic vs Exothermic