Kinetics 1 Flashcards
What is the activation energy?
Minimum energy which particles need to collide to start a reaction
What does a higher concentration of particles result in?
An increased frequency of collision
What does orientation of collision mean?
The particles will only react if they hit each other the right way round
e.g.
When HCl reacts with ethene, the H of the HCl has to approach the double bond in ethene and in any other collision, they would just bounce off each other
What is the Maxwell Boltzman energy distribution?
It shows the spread of energies that molecules of a gas or liquid have at a particular temperature
How can particles gain energy?
Increase in temperature
Through collisions
What does the area under the curve represent in the maxwell boltsman distribution?
The total number of particles present
This should always remain constant as the total number of particles is constant
Where should the maxwell boltzman distribution start?
At the origin as there are no molecules so no energy
Why do some particles have low energies at the beginning of the maxwell boltzman distribution?
As collisions cause some particles to slow down
What is the Emp and where does it occur on the maxwell boltzman distribution?
This is the most probable energy and occurs at the peak
Where is the mean energy on the maxwell boltzman distribution?
Not at the peak but a little after
Where do most molecules have energies on the maxwell boltzman distribution?
Between the 2 extremes but the distribution is not symmetrical
How many particles have energy greater than the activation energy on the maxwell boltzman distribution?
Only a few
Why should the energy distribution never meet the x-axis on the maxwell boltzman distribution?
As there is no maximum energy for molecules
What happens to the maxwell boltzman distribution as temperature increases?
It shifts to having more molecules with higher energies
What happens to the Emp and the mean energy at higher temperatures on the maxwell boltzman distribution?
They shift to higher energy values although the number of molecules with these energies decrease
What is the range of energies like on the maxwell boltzman distribution at higher temperatures?
It is wider
What happens to the energy of the particles at higher temperatures?
It increases
What will increasing surface area do to the rate of reaction?
Increase it as it will cause succesful collisions to occur more frequently
What happens given that particles have a higher energy at higher temperatures?
They collide more frequently and more often with energy greater than the activation energy
More collisions result in a reaction
What happens to the rate of reaction at higher concentrations?
- More particles per unit volume
- Particles collide with a greater frequency
- Higher frequency of effective collisions
What happens to the shape of the energy distribution curves if concentration increases?
The shape does not change (Mean and Emp don’t change) but the curves will be higher and the area under the curves will be greater as there are more particles
When concentration increases, do a greater proportion of molecules have energy greater than the activation energy?
No - although the curve has shifter upwards so more molecules have energy > activation energy, ther are more molecules in total, so the proportion does not change
What do catalysts do?
Increase rate of reaction without getting used up
How do catalysts increase the rate of reaction?
By providing an alternative route or mechanism with a lower activation energy
How does adding a catalyst affect the energy distribution curve?
If the activation energy is lower, more particles will have energy greater than the activation energy, so there will be a higher frequency of effective collisions and reaction will be faster
