AP chem unit 6 cram

Kinetics

The study of the speed (rate) of chemical reactions and the factors affecting it.

Reaction rate on a graph

The slope of the graph of concentration vs. time shows the speed of the reaction.

How does the rate change during a reaction?

Reaction rates decrease over time as reactant concentrations drop.

Collision Theory

For a reaction to occur, reactant particles must collide with enough kinetic energy and proper orientation.

Effective collisions

Collisions that form products by breaking bonds.

Ineffective collisions

Collisions that do not result in product formation.

Activation energy (Ea)

The minimum energy required for reactants to form an activated complex and proceed to products.

Catalysts

Substances that lower activation energy, increasing reaction rate by providing an alternative pathway.

Dynamic equilibrium

A state where the rate of the forward reaction equals the rate of the reverse reaction, with no net change in concentrations of reactants and products.

Equilibrium concentrations

Amounts of reactants and products at equilibrium, which may differ but concentrations remain constant over time.

How is Kc Calculated?

Kc= products / reactants raised to their coefficients

how is Kp calculated?

Kp = products (in atm (pressure)) / reactants (in atm) raised to their coefficients

what is the relationship between Kc and Kp?

Kp=Kc(RT)^nwhere n is the change in moles of gas.

n= Moles of products - Moles of reactants

Reaction quotient (Q)

Indicates the direction of the reaction;

shifts right for increased products,

left for increased reactants, and is at equilibrium when Q equals K.

Le Chatelier’s Principle

When a system at equilibrium is disturbed, it shifts in the direction that counteracts the disturbance.

if the reactant concentration increases it shifts…?

right (forward)

If the product concentration increases it shifts…?

left (reverse)

endothermic

Increase temp → shift right, increases.

Decrease temp → shift left, decreases.

exothermic

Increase temp → shift left, decreases.

Decrease temp → shift right, increases.

in pressure; volume decreases, what happens to the moles?

reaction shifts to fewer moles of gas

in pressure; volume increases, what happens to the moles?

reaction shifts to more moles of gas

Common Ion Effect

When adding an ion common to a reaction, equilibrium shifts to reduce the concentration of that ion.

General rate law

An equation that relates the rate of reaction to the concentration of reactants, where the reaction orders are determined experimentally.

Zero-order reaction

Rate is independent of concentration.

First-order reaction

Rate is directly proportional to concentration.

Second-order reaction

Rate is proportional to the square of concentration.

ICE Table Method

initial concentrations (moles)

changes, (coefficient and x) ( SUBTRACT X FOR REACTANTS

; PRODUCTS ADD X)

expressions for equilibrium concentrations ( moles +or - X)

if temperature increases, what happens to the reaction?

Endothermic (the reaction absorbs the heat); heat is a reactant

if temperature decreases, what happens to the reaction (type)?

Exothermic (the reaction releases heat); heat is a product