Lecture 4 Flashcards
The collision theory
For a reaction to occur molecules must collide.
Assumes the rate of the reaction is proportional to the number of molecular collisions per second
What do molecules need to have an effective collision?
1) Molecules must have proper orientation towards each other
2) Molecules must have enough energy to break bonds (Activation energy)
Activation energy?
Minimum amount of energy to initiate a chemical reaction.
Low temperature has _____ rate
slow
Less energy fewer collisions
High temperature has ____ rate
fast
More energy more frequent collisions
Rate of Reaction equation
aA + bB –> cC + dD
Rate of reaction = -1/a(A/t) = - 1/b(B/t)
.. ect for rest of equation
Why do reaction slow over time?
Depletion of reactants, temperature changes, loss of catalyst, decrease in number of collisions
Rate law expression
Rate = K[A]x[B]y
The larger the K value…
The faster the reaction
Reaction Order??
Radioactive decay
Large range of half-lives
Photodissociation
Absorption of photon
Pseudo first order
A reaction that should be 2nd order but the B reactant is in higher concentration than A so its first order
Unimolecular
a single molecule dissociates
Biomolecular
the collision of 2 molecules
