Chemical Kinetics Flashcards
How to calculate the concentration of A, given initial concentration and k for a first order reaction?
c(A) = c0(A) e^-kt
What does the reaction order of a single step mechanism tell us about the reaction?
number of molecules that react in this step (rate determining step), so how fast the reaction is
How to calculate c(A) given k and c0(A) for 0-order?
c(A) = -kt +c0(A)
How to calculate c(A) given k and c0(A) for 2nd Order?
1/[A] = kt + 1/ [A]0
Do First and second order reactions occur in dependence of geometry?
No, no dependence
Does Reaction equation have anything to do with reaction law (rate equation)?
no. rate law is determined experimentally
What are the requirements for an effective collision?
- E(kin) > Ea
- INELASTIC collision with reaction
What are the basic assumptions of the collision theory?
- Move faster with increasing temperature
- faster molecules cause higher COLLISION frequency
- precondition: must collide
- reaction rate increases as collision frequency increases
- sufficient Ea needed
According to the collision theory the reaction rate increases with increasing temperature. Explain this by means of a diagram
diagram
How did Hammond Postulate allow to make assumptions about the structure of transition states?
- in an exothermic: looks more like reactants
- in an endothermic: looks more like products
DIAGRAM
What is Arrhenius Equation?
k = Ae^-(Ea)/RT
How does a catalyst change the reaction rate?
by lowering the activation energy, increases rate.
- remains unchanged
What is a single step mechanism?
only has one step to complete reaction, through a single transition state
What is homogeneous catalysis?
reactants and catalyst are in the same phase
what is heterogeneous catalysis?
reactants and catalyst are in different phases
