Chem202 Chap 14 & 15

Average reaction rate for

rate=-^A/^trate=^B/^t^ is delta

Stoichiometry and Reaction Rate


rate law


reation order and units of k

1st order half life

half life of a first order reaction is independent of the initial concentration of the reactant.

2nd order half life

half life is inversely proportional to initial reactant concentration.

0 order half life


collision theory

the reaction rate is directly proportional to the number of molecular collisions per second. ratea=number of collisions/s

activation energy Ea

minimum amount of energy required to initiate a chemical reaction.

activated complex or transition state.

when molecules collide in an effective collision. highest amount of potential energy.

unimolecular elementary reaction

one reactant moleculesA------>products

bimolecular elementary reaction

two reactant moleculesA+A---->productsA+2B---->products

termolecular elementary reaction

three reactant moleculesA+B+C--->products

reaction order for each reactant in an elementary reaction is equal to its stoichiometric coefficient in the chemical equation for that step.



is a substance that increases the rate of a chemical reaction without itself being consumed.

heterogeneoues catalyst

the reactant and the catalyst are in different phases. The catalyst is usually a solid and the reactants are either gases or liquids

homogenous catalyst

the reactants and the catalyst are dispersed in a single phase usually liquid

Reversible process

A chemical reaction in which the products can also be consumed to produce reactants, a process known as the revers reaction


the condition where the forward and reverse reactions are occurring at the same rate and there is no net change in the reactant and products concentrations over time

Reaction Quotient (Qc)
(also Kc at equilibrium)

is the product of the product concentrations over the product of the reactant concentrations with each concentration raised to a power equal to the corresponding stoichiometric coefficients in the balanced chemical equation. Law of Mass Action

Equation reversed = 1/Kc1
Equation mulitplied by 2 =(Kc1)2
Two equations added = Kc1*Kc2

Delta n=number of moles of product-number of moles of reactant

raised to the power of the coefficient in front

if Qc<Kc ---Reactant to products
if Qc>Kc ---Products to reactants

+prod shift left-prod shitf right+react shift right-react shift left

+ pressure-----shift equil to side w/ fewest moles
+volume-----shift equil to side w/ most moles

temp is the only factor that changes the equilibrium constant

catalyst shifts neither the equilibrium or equilibrium constant