Chemistry - Chemical Kinetics

Rate expression

Rate law

m and n must be determined experimentally

• Find where rate changed in one and stayed the same in the other

• divide rate and concentration

• set concentration to the power of m equal to rate

  • concentration^ m = rate ; solve for m

• do the same for other variable

Zero order linear graph

First order linear graph

Second order linear graph

Delta H Graph; Endo or Exothermic?; Where is transition states and intermediate?; Where is Ea1 and Ea2?

What is the rate determining step; how do you see it in the Delta H graph?

• slowest step

• The step with the largest Ea

Are catalysts consumed in a reaction?

no they are regenerated

What are protein catalysts called?

Enzymes

How do catalysts speed up a reaction?

By lowering a reactions activation energy (Ea)

(not by changing the energy levels of the reactants or products)

How do catalysts lower Ea?

by providing an alternative pathway (different mechanism) between reactants and products

Do catalysts shift equilibrium reactions?

no

Collision Theory

• Molecules have to collide to react

• The greater the number of collisions per second, the greater the chance that molecules will hit each other

• Molecules must hit each other with at least Ea

• Increasing temperature can increase a molecules speed

Must molecules hit each other is the correct 3 dimensional orientation?

yes

As temperature goes us, k (rate constant) and reaction rate go?

up and up

If K (rate constant) and reaction rate go up, Ea goes?

down

What is the rate determining step?

• the slow step

When given elementary steps how do you find the intermediate?

• substance produced in the middle of the reaction that get used up before the product

• They get cancelled out along the way

When given elementary steps, what is the overall rate?

• Rate = k * the concentration of each reactant in the slow step multiplied by each other

When given elementary steps, what is the overall reaction?

• Add up elementary steps and cancel out intermediates