kinetics Flashcards
Define activation energy
The minimum energy needed for a reaction to occur
What must happen did a reaction to occur
Particles must collide
With E >Ea
Why do most collisions not cause a reaction
A small number of particles have E > Ea
If a reaction occurs very slowly because only a small number of particles have E>Ea why will all of the reactants eventually gain enough E every to react
Molecules gain energy
Due to collisions
Why do do some particles only have a very small amount of energy
Collisions
Cause some molecules to slow down or lose energy
What is the rate of reaction
The rate of change in concentration
Per units of time
The rate of reaction is only influenced by
Temperature
Concentration
Pressure (for gas based reactions)
Catalysts
Surface area (for solid reactants, as surface area increases, rate of reaction increases)
What is a catalyst
A catalyst is that a substance that increases the rate of reaction
But is not used up or changed
How does a catalyst work
By providing an alternative reaction pathway
That has a lower activation energy
A catalyst increases the rate of reaction because :
The activation energy decreases
So more of the particles have a collision energy greater than the activation energy R> Ea
So more frequent successful collisions
Temperature increase, the rate increases due to :
More particles have E> Ea
Increases frequency of successful collisions
Concentration increases, rate increases due to :
Increase in number of particles per unit volume
Increase frequency of successful collisions
Pressure increases, rate increases due to :
Increases in number of particles per unit volume
Increases frequency of successful collisions
Catalyst added , rate increases due to :
Lowers Ea
So more particles with E> Ea
Increases frequency of successful collisions
Surface area increased, rate increases due to :
Increased number of reactant particles made available
Increases frequency of successful collisions
