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36 terms

Chapter 13: Kinetics: Mechanisms and Rates of Chemical Reactions

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Way to determine rate of overall chemical reaction
Determined by rates of elementary reactions
Rate determining step
Elementary rxn that proceeds slower than any of other steps in mechanism. Governs rate of overall chem rxn.
kinetics
study of rates of chem rxns
kinetic units
M/s-1
The reason stoichiometry isn't used for rate law for a reaction.
because orders must be determined experimentally
Cases where stoichiometry is acceptable to determine rate law.
Single elementary steps and rate limiting steps.
Three concepts of reaction mechanisms and rate laws.
. Mechanism is one or more elementary reaction that describes how chem reaction occurs
sum of individual steps of mechanism gives balanced stoichiometric chem equation
rate law predicted by mechanism is same as experimental rate law.
Units for zero order
Ms-1
units for first order
s-1
units for second order
M-1s-1
specific heat of water?
4.184 C
(5/9)(f-32)
F to C
concentration reactant at the beginning, concentration remaining at time t, and rate constant.
In the Order reaction equations what does [A]o, [A], and kt stand for?
first order
the linear order
ln([A]o/[A])=kt
first order reactant eqn
Half life
amount of time required for half the amount of reactant to be consumed
the original concentration, [A]o
In first order reactions, what is half life independent of?
t(1/2)=ln2/k
WHAT'S HALF LIFE FORMULA?
reciprocal of concentration varies linearly with time
second order reaction graph
concentration varies linearly with time
zero order
By examining how concentration changes
how can rate laws be determined?
unimolecular fragmentation
energy of products is always higher than that of reactants
unimolecular rearrangement
the energy always rises initially, but as bond forms, energy decreases.
0.0821, 8.314
the two "R" constants
reaction mechanism
Sequence of molecular events
molecular event during chem rxn with 1-3 reactants
Elementary reactions
Most common elementary reaction. Collision of two reactants
bimolecular reaction
unimolecular reaction
Elementary reaction where a single molecule breaks into two pieces and rearranges into a new isomer
termolecular reaction
Elementary reaction where three chem species collide simultaneously. Very rare.
Chemical species produced in early step of a mechanism and consumed in a later step. Never appears in overall reaction.
Intermediates
molecular events/time
Define rate of reactions
Rate determining step
elementary rxn that procedes more slowly than any other step in mechanism. Governs overall chem rxn.
kinetics
study of rates of chem rxns.
units of kinteics
Ms-1
unimolecular rxns slow down
When less reactant molecules remain.
rate=k[A]x[B]y
rate law skeleton