Kinetics (Difficult to involve rate determining step) Flashcards
What is kinetics
The study of the factors that affect rates of chemical reactions
Collision theory
For a reaction to take place between 2 particles, they must collide with enough energy and correct orientation to break the bonds
Factors that affect rate of reaction
Increase temp
Increase concentration (solution)
Increase pressure (gas)
Increase surface area (solid)
Use a catalyst
Activation energy
The minimum energy required to start a reaction
On an enthalpy diagram, what is the species at the top of the curve called
A transition state OR activated complex
What does the maxwell-boltzmann distribution tell us
No particles have 0 energy
Most particles have intermediate energy - around peak of curve
Few have very high energy, there is no upper limit
Average energy is not the same as most probable
Effect of temperature on Maxwell-Boltzmann distribution
At high temp, peak of the curve is lower and moves to the right. Number of particles with very high energy increases.
Greater area or particles past the activation energy - more successful collisions
Total area under curve remains the same of all temps with same particle number
Catalyst
Substance that affect the rate of chemical reactions without being chemically changed themselves at the end of reaction. Provide alternative pathway
How do catalysts work
Reduces activation energy
Catalyst effect on maxwell-boltzmann distribution
Shift activation energy left
X and Y axis on maxwell
X = energy
Y = Fraction of particles with energy
What do catalysts not effect
Enthalpy change
Position of equilibrium
2 stages of catalytic converter reaction
Adsorption - gases form weak bonds with metal atoms of catalyst
Desorption - Products break away from atoms
Equation for rate of reaction
Change in conc / time
What is the rate expression equation
Rate = k[X][Y]^2
