Chem202 Chap 14 & 15


Average reaction rate for
A----->B


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


Stoichiometry and Reaction Rate
aA+bB---->cC+dD


rate=-1/a(^[A]/^t)rate=-1/b(^[B]/^t)rate=1/c(^[C]/^t)rate=1/d(^[D]/^t)


rate law
aA+bB---->cC+dD


rate=k[A]x[B]y


reation order and units of k
0====M/s
1====1/s
2====1/Ms
3====1/M2s


1st order half life
t1/2=.693/k


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


2nd order half life
t1/2=1/k[A]o


half life is inversely proportional to initial reactant concentration.


0 order half life
t1/2=[A]o/2k


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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.


A+A---->products2A------>productsrate=k[A]2


catalyst


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


Equilibrium


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)
Qc=[C]c[D]d/[A]a[B]b
(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


Kp=Kc(RT)^n
Delta n=number of moles of product-number of moles of reactant


Kc=prod/react
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