unit 5 ap chemistry

rates

defined by stoichiometry in balanced chem equations

what can rates be affected by

temperature, concentrations, catalyst, etc

does temperature affect activation energy

no

what does temperature affect

average kinetic energy

if temperature is lowered

particles, ke, and speed will be lowered

exothermic

products is lower than reactants on potential energy diagram

endothermic

products is higher than reactants on potential energy diagram

activation energy

activation energy = activation complex - reactants

activated energy

highest point from reactants

activated complex

bonds partially formed and are broken to create the new products

what happens as activation energy increases

higher activated complex and reaction rate decreases

axes on pe diagram

potential energy (y) and reaction coordinate (x)

collision theory

1. collide

2. sufficient energy

3. correct orientation for reaction

what happens when catalyst is used in pe diagram

ea decreases, rr increases, more collisions

how to distinguish elementary step

1. clearly indicated

2. clearly part of multi-step mechanism

catalyst in reaction mechanism w/ elementary steps

beginning and end of the mechanism

intermediate in reaction mechanism w/ elementary steps

product of step 1 to reactant of step 2

creating balanced equations based on elementary steps

1. get rid of intermediates from each step

2. combine like terms

rate law dependent on

concentration of given reactant

elementary reaction

single event or step through combining all steps

how to find order of reaction without table

1. cannot determine if it is not in elementary

2. if in elementary, use stoich coefficients for the reactants to determine the order

how to get rid of intermediate of fast equilibrium

1. find rate law of both reactant and product of the FAST STEP

2. equal them to each other

3. substitute the intermediate into the slow step intermediate

catalyst

must be at least two step mechanism

reacts in step 1 and regenerated in another step later on

which step has the highest activatino energy

slow step

if given graph, how to find the rate law

find constant, divide second by first experiment to find exponent

if same base and exponent, it’s first order reaction

exponent of 2 after dividing, it’s second order reaction

half life first order

0.693/k

first order

consistent rate decreases

double order

doubles increases

units of k in zero order

m/s

units of k in first order

1/s

units of k in second order

ms^-1

relative rate vs concentration of zero order

stays constant, no increase or decrease