Lecture 4: Reaction Rates and Temperature Flashcards
Arrhenius equation; finding Ea and A know the units of R, T, A, k, Ea Collision theory Moelcularity Unimolecular elementary reaction Bimolecular elementary reaction Termolecular elementary reaction elementary reaction Transition state factors affecting transition state reaction mechanism
state Arrheinius equation
k = Ae^-Ea/RT
what is k in Arrhenius equation (AE)?
rate proportionality constant (rate constant)
A ?
pre exponential factor
T ?
temperature in Kelvin (therefore add 273.15 to Tc)
Ea?
activation energy
R ?
gas constant R= 8.31451…
units of A ?
mol L-1 s-1
units of T ?
Kelvin (K)
units of R ?
J-1 K-1 mol -1
Ea ?
J-1 mol -1
What does the collision theory of chemical reactions state?
it assumes that molecules react by the making and breaking of bonds, to do so it must collide with SUFFICIENT ENERGY and in the correct orientation
What is an elementary reaction?
the step where molecules collide
What gives the order of an elementary reaction?
the molecularity of the reaction
What is an elementary reaction equal to?
the order for each reactant is equal to its moelcularity
Define molecularity?
the number of COLLIDING entities that are INVOLVED in a single reaction step
What are the types of elementary reaction?
unimolecular
bimolecular
termolecular
What does it mean by unimolecular elementary reaction?
where a SINGLE molecule REACTS with ITSELF
What does it mean by bimolecular elementary reaction?
where TWO moleules meet and collide
What does it mean by termolecular elementary reaction?
where 3 molecules meet and collide
What is the RATE of an elementary reaction dependent on?
the rate of collisions
What factors increase the rate of collision?
temperature concentration of reactants physical state of reactants presence of catalyst presence of light nature of reactants
What is a reaction mechanism?
a series of elementary reactions leading to overall reaction
What is the transition state?
in an elementary reaction, it is the point of highest energy between reactants and products
What does it mean by reactive inermediates?
are short lived reactive species that appear in one step and react in a later step in the reaction mechanism
