Controlling The Rate Of Reaction Flashcards
How do you work out the relative rate ?
The units are (s-1) .
The equation is R=1/T
Time measurements can be used to compare reactions
How do you work out the average rate?
Average rate = change in quantity divide by change in time
Units are cm3s-1 for volume, gs-1 for a mass, and molL-1 for a concentration
What is the relationship between time and rate?
As the rate of reaction increases, the time taken for the reaction decreases
Why is it important to be able to control the rate of reaction in industry ?
In industry the rate must be controlled to ensure they are economically viable
(Too high = explosion, too low = bad)
What must happen in order for a reaction to take place ?
- reactant particles have to collide
- collide with sufficient energy
- collide with correct geometry
What does a potential energy diagram show?
Draw a curve
- start to the top is the activation energy
- the enthalpy change is start to end value
- reactants in, products out
What is the activation energy
.this is the minimum energy required for a reaction to occur I.e. the energy by colliding particles to form an activated complex. Units are KJmolL-1
What is the activated complex
It’s a highly unstable. It is the maximum point on the reaction path
What is the enthalpy change
The enthalpy change shows the amount of heat energy released during the reaction. Therefore in an exothermic, reaction the enthalpy change is negative and an endothermic reaction it is positive. An endothermic reaction takes in heat energy and an exothermic reaction releases heat energy
(Rate of reaction isn’t effected by enthalpy change)
What factors effect rate of reaction
- concentration
- pressure
- surface area
- temperature
- collision geometry
- catalyst
How does particle size effect rate of reaction
.as the particles size decreases the surface are increases. A smaller particle size of a reactants provides a greater surface area, that collisions can take place on. (Therefore more collisions per seconds so reaction rate increases)
How does concentration effect reaction?
.if the concentration of reactant particle is increased then there are more reactant particles moving together. So there will be more collisions per second. Hence the increase in the reaction rate. As time of a reaction increases the concentration decreases, hence why the rate decreases
How does pressure effect rate of reaction?
An increase in pressure results in an increase in the number of reactant particles in the same volume. This results in more reactions per second and therefore an increased rate of reaction
How do catalysts effect the rate of reaction
A catalyst can lower the activation energy and increase the rate of reaction
How does collision geometry effect rate of reaction ?
.in order for a reaction to occur particles must collide at the correct collision geometry
