Chapter 19Reaction Rates

AndEquilibrium

RatesMeasures the speed of change over an interval of time

Collision TheoryAtoms, ions, and molecules can react to form products when they collide with enough kinetic energy.

Activation EnergyThe minimum amount of energy that particles must have to react.

Transition StateThe point at the peak of the activation energy where compounds change back to reactants or form new products.

4 Factors affecting Reaction Rates

1.Temperature: Increase in temperature = increase in KE, w/more KE one has more and harder collisions causing more product to form

2. ConcentrationMore molecules means greater chance of collision resulting in the formation of new products.

3. Particle Size(increased surface area)

The more surface area you have the greater the chance of collision.

4. CatalystA substance that speeds up a reaction without being used up in that reaction.Usually written above the yields sign in an equation.

InhibitorsWorks against the catalyst.

Reversible ReactionsThe reaction occurs in both directions at the same time.

2 SO2 + O2 2 SO3

Chemical EquilibriumA state at which the forward and reverse reaction occur at the same rate.

**DOES NOT MEAN**Same amount of product and reactant formed.

LeChatlier’s PrincipleIf stress is applied to a system in dynamic equilibrium, the system changes to relieve the stress.

ConcentrationIncreasing the concentration will always change the equilibrium away from the increased concentration.

H2CO3 CO2 + H2O

TemperatureEquilibrium shifts in the direction that absorbs the heat

2 SO2 + O2 2 SO3+ Heat

Pressure (in gasses)

Only affects equilibrium if there is an unequal # of moles. Equilibrium moves to the side w/less moles.

K(eq) Equilibrium Constant

The lower case letters = # of moles of that compoundaA + bB cC + dD

K(eq)=[C]c

x [D]d [A]a

x [B]b

K(eq) Equilibrium ConstantIt shows whether products or reactants are favored in the reaction.K(eq) > 1 Products are favored

K(eq) < 1 Reactants are favored