AQA A-Level Chemistry (new spec) 1.5 Kinetics

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Cards (29)

What is the collision theory?
Reactions can only occur when collisions take place between particles when they have sufficient energy
Define activation energy
The minimum energy needed for particles to collide to start a reaction
What does the Maxwell Boltzmann distribution show?
The spread of energies that molecules of a gas or liquid have at a particular temperature
Why should the energy distribution go through the origin on the graph?
There are no molecules with no energy
What is the Emp?
Most probable energy
Where is the Emp line on the graph?
From the peak down to the X-Axis
What does the area under the curve represent?
The total number of particles present
Why should the energy distribution never meet the x-axis?
Because there is no maximum energy for molecules
What is the label for the y-axis?
Number of molecules within a given energy
What is the label for the x-axis?
Energy
What happens to the particles when the temperature is increased?
More particles will have energy greater than the activation energy
What does Ea stand for?
Activation energy
What happens to the peak of the Maxwell Boltzmann distribution when the temperature is increased?
It moves to a higher energy with a lower height
What happens to the proportion of molecules exceeding the activation energy when the temperature is increased?
The proportion of molecules increases
What happens to the Emp and mean energy when the temperature increases?
They shift to high energy values
Why should the total area under the curve remain constant when the temperature is increased?
The total number of particles stay constant when temperature is increased
In terms of collision theory, what happens to the particles when temperature is increased?
The energy of the particles increases, meaning they collide more frequently with energy greater than the activation energy. More collisions = more reactions
What happens to the range of energies of the molecules when the temperature is higher?
The range of energies is wider
In terms of the collision theory, what happens to the particles when the concentration is increased?
There are more particles present so the particles collide more frequently
What happens to the mean and the Emp when the concentration is increased? 
They stay the same
Will the area under the curve differ when the concentration is increased?
Yes because there are more particles, meaning the peak will be higher
In terms of the collision theory, what happens to the particles when the surface area is increased?
It causes collisions to occur more frequently, increasing the rate of reaction
What do catalysts do?
They increase reaction rates by providing an alternative route with a lower activation energy?
Are catalysts ever used up?
No
What is Ec?
Activation energy with a catalyst
What happens to the proportion of molecules exceeding the activation energy when a catalyst is present?
The proportion increases as the activation energy is lower
What happens to the rate of reaction when a catalyst is introduced?
It increases
Define the rate of reaction
The change in concentration of a substance in unit time.
What is the initial rate?
The rate at the start of a reaction