Summary Chapter 7&17, Equilibrium (IB Chemistry)

RATE EQUATIONS RATE DETERMINING STEP
COLLISION THEORY
·


A(aq) + Blaq) -
> ((ag) + D(ag) • RATE DETERMINING STEP: is the SLOWEST STEP in the reaction
• collision frequency -
n-> rate of
• MOLECULARITY: number of reactant particles that participate in the rate-

• collision energy Rate GLA]* (B] order
determining step
·



=
on
> concentrations of
↳ • UNIMOLECULAR - one species involved in the rate-determining step
• activation energy reactants
• BIMOLECULAR - two species involved in the rate-determining step
• collision geometry
ORDER OF REACTION • can be identified from a rate equation given that the reaction mechanism is known
RATE OF REACTION • the power to which the concentration of that reactant is raised • the rate-determining step must have the greatest activation energy
in the rate equation • highest activation energy = slowest step (big peak in the graph)
• units: mol dm^3s^-1 • Order of reaction = 0, if there is no affect in changing of
concentration
change in amount of reactants products (modste MECHANISM PROBLEMS
rateof - • Order of reaction = 1, if there is directly proportional to the rate
or



Time (s) • ELEMENTARY STEPS: the steps involved in a reaction mechanism
of reaction (ex, doubling) D
A + B - C +

• Order of reaction = 2, if the rate is directly proportional to the



·
• involve the formation of an intermediate
square of the concentration of that chemical (ex, concentration 1 R D
1
Elementary Step
:
- +

doubles increases rate of reaction by factor 4)
R+ B > C
Elementary Step
-
2 :




RATE CONSTANT THE ARRHENIUS EQUATION
Techniques used to measure rate of reaction:
• at higher temperatures: the rate of reaction increases, the rate constant increases
• mass loss
• Gas production h =

Rate(B] • EQUATION:

i constant
• Colorimetry rate
constant-k = Aegas
↳ units : mol"dm's
↑ Arrhenius constant

BOLTZMANN DISTRIBUTION CURVE • GRAPHING
YT(k -)




I
• a graph that shows the distribution of energies at a A
certain temperature
Ink = +




Inl
y
=



TEMPERATURE: In k
x =
i
• an increase in temperature of a reaction mixture results


maCradieHet
in an increased mean energy of the molecules so there
is a wider spread of values
R


• there is an increase in reaction rate as a greater
proportion of molecules have energy equal to or greater
than the activation energy • CALCULATING THE ACTIVATION ENERGY


CATALYST:
• proportion of molecules with low energies which cannot
react
In h = )
• Proportion of molecules that have energy greater than
the activation energies, Ea