1. Reaction rates & equilibria
A survey

2. Collision Theory
Products form when reactants collide with each other, providing they have enough energy to overcome any activation requirements (energy of activation)
This may be expressed as amount of reactants changing per unit time
Activated complex: an unstable arrangement of atoms that forms momentarily at the peak of the activation energy barrier; may also be called the transition state

3. Factors that affect reaction rate
Temperature: usually raising temperature increases reaction rates
Concentration: in a fixed volume, increased concentration usually increases reaction rates
Particle size: an increase in surface area increase reaction rate
Catalysts: create a lower energy pathway
Inhibitor: a substance that interferes with a catalyst

4. Equilibria Most reactions are reversible, but degree is variable
Chemical equilibrium: when the forward and backward reaction rates are equal, so that no further change is occuring
Equilibrium position: this indicates whether the reaction tends to go forward or backward…shown by the lengths of the direction arrows between reactants and products

5. Factors affecting equilibrium
LeChatelier’s Principle
If a stress is applied to a system, the system will change in some way to relieve the stress
Concentration: adding or removing either a product or reactant
Temperature: depends upon whether heat is a product or reactant
Pressure: only affects gaseous equilibria; depends upon volumes on each side of equation

6. Equilibrium Constants
aA + bB  cC + dD
Equilibrium constant is the ration of product concentrations to reactant conc.
Keq = [C]c · [D]d/ [A]a · [B]b
If Keq >1, products favored at equilibrium
If Keq <1, reactants favored at equilibrium

7. Solubility Equilibria
Solubility Product Constant: Ksp
Salt: AB(s)  A+ (aq) + B- (aq)
Keq = [A][B]/[AB], but since AB is a solid, we consider it to be a constant, so:
Ksp = [A][B]
The smaller the numerical value of Ksp, the lower the solubility of the compound.

8. Common Ion Effect
The addition of a common ion, found in both salts in a solution, will cause the solubility of one of the salts to decrease