3.2.2 - Reaction rates Flashcards
Define activation energy
The minimum amount of energy which particles need to collide to start a reaction.
show the Ea of an exothermic reaction
Always between reactants and top part of the curve.
Draw a boltzmann distribution curve showing most likely energy and mean energy particles have
Draw a boltzmann distribution curve with everything you know about it
Effect of increasing temp on the boltzmann distribution curve
The red line is higher temp
- Make sure red and blue line DO NOT TOUCH
Effect of catalyst on boltzmann curve
If the activation energy is lower, more particles will have energy > EA, so there will be a higher
frequency of effective collisions. The reaction will be faster
- catalyst is 1 line, temp is 2 lines
Using the Boltzmann distribution model, explain how the rate of a reaction is affected by
temperature - ppq
Curve
- Curve starts within one small square of origin
AND curve does not touch x axis at high energy
AND curve does not increase by more than one small square at higher energy ✓
Labels
Axes labels correct:
Y - Number of molecules AND x - Energy
Curves for two temperatures
- Drawing of two curves with higher and lower temperature
clearly identified in diagram or text
AND higher T maximum to right AND at least one small square
lower than lower T ma
Using the Boltzmann distribution model, explain why the rate of a reaction increases in the
presence of a catalyst. - ppq
Curve starts within two small squares of origin
AND
not touching the × axis at high
energy ✓
axes labels:
y: (number of) molecules/particles
AND
x: (kinetic) energy ✓
Why does pressure affect rates
Why does concentration affect rates
What do catalysts do
Catalyst lowers the activation energy (by providing an alternative route) ✓
- (With a catalyst a) greater proportion of molecules with energy
greater than activation energy
Blurt everything you know a heterogeneous catalyst
- Different phase or state to the catalyst.
- Increasing the surface area (by turning a solid catalyst into a powder) will increase the rate of reaction as more particles can react with the catalyst at the same time.
Blurt everything you know a heterogeneous catalyst
When catalysts and reactants are in the same phase,
the reaction proceeds through an intermediate species.
e.g when you did the nucleophilic substitution of the benzene rings and you had to reform the catalyst again (metal carrier)
Benefits of using catalyst
- Environmental benefits
- Reduce CO2 emissions
- Less waste
