Kinetics I Flashcards
In order for a reaction to take place it must have
“the right conditions
Collide in the correct orientation
Collide with sufficient energy know as Ea”
In terms of collision theory, describe the effect in an increase of concentration
At higher concentrations there are more particles per unit volume and so the particles collide with a greater frequency and there will be a higher frequency of successful collisions.
In terms of collision theory, describe the effect of an increase in temperature
At higher temperatures the kinetic energy of the particles increases. They collide more frequently and more often with energy greater than the activation energy. More collisions result in a reaction
In terms of collision theory, describe the effect in an increase in pressure
At higher pressures there are more gas molecules per unit volume and so the particles collide with a greater frequency and there will be a higher frequency of successful collisions.
In terms of collision theory, describe the effect in an increase in surface area
Increasing surface area will cause successful collisions to occur more frequently between the reactant particles and this increases the rate of the reaction.
How do we calculate the ROR from data showing the time taken from a reaction?
rate of reaction =
Δ[reactants or products] / Δ time mol dm-3s-1)
How do we calculate the ROR from the gradient of a graph ?
draw a tangent at the point specified and use Change in y over change in x
What is the Maxwell Boltzmann Distribution?
The Maxwell-Boltzmann energy distribution shows the spread of energies that molecules of a gas or liquid have at a particular temperature
How can a reaction go to completion if few particles have energy greater than EA?
Particles can gain energy through collisions
In a MBD the area under the graph represents
the total number of particles present
Where can’t we look at when searching for the mean energy in a MBD graph?
“Not the peak of the curve
The mean energy of the particles”
On a MBD would the energy distribution go through the origin?
The energy distribution should go through the origin because there are no molecules with no energy
What does the peak in the MBD represent?
Emp this is the most probable energy (not the same as mean energy)
In a MBD, are there lots of particles with energy greater than the Ea?
No only a few particles have energy greater than the EA
In terms of MBD, how does change in temperatures affect ROR.
As the temperature increases, the graph shows that a significantly bigger proportion of particles have energy greater than the activation energy, so the frequency of successful collisions increases vice versa
What is the role of a catalyst?
“Catalysts increase reaction rates without getting used up.
They do this by providing an alternative route or mechanism with a lower activation energy”
Describe the action of a catalyst in terms of MBD
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
Define homogeneous reactions
is one that takes place in a single phase
Define heterogeneous reactions
is on me which the reactants are in two phases
The use of a solid catalyst for industrial reactions in the gas phase
The surface area of a solid in a heterogenous reaction is increased (by decreasing the particle size) there’ll be more surface for the reactants to react. This causes more frequent successful collisions increasing ROR.
What are the economic benefits of the use of a catalyst in industrial reactions?
they allow the reactions to process at a fast rate at a much lower temperature. This reduces the costs energy since there’ll be less heat heat lost at lower temperature temperature Because the reaction is faster, more products will be produced in a shorter time. This increases efficiency and costs of the process
Define the term activation energy
The minimum amount of energy which particles need to collide to start a reaction.
