P2 - 6.2 Factors Affecting Rates of Reaction & Collision Theory Flashcards
The Rate of Extent of Chemical Change
What are the 4 main factors that affect the rate of chemical reactions
- temperature
- concentration/pressure
- surface area
- presence/absence of catalyst
What is collision theory
For particles to react they have to collide with each other with sufficient energy (activation energy)
In collision theory what is another way of saying sufficient energy
Activation energy
What happens if chemicals collide with less energy than activation/sufficient energy
Nothing will happen because there is not enough energy
What is activation energy
The minimum amount energy required for a chemical reaction to take place
What will the rate of reaction depend on in collision theory
1) amount of energy particles have
2) frequency of collisions
How does the amount of energy particles have affect the rate of reaction in collision theory
If particles have more energy it will mean they can move faster and transfer quicker during the collisions
How does the frequency of collisions effect the rate of reaction in collision theory
Not all collisions are successful however the more they collide the more successful collisions become
True or False: particles dont always reach activation energy
True
True or False: the more particles collide, the less successful they become
False
The more often particles collide, the more successful collisions will become
How does collision theory have an effect on the rate of reaction
They can increase the rate of reaction by having more successful collisions
If temperature is increased, how will this effect the rate of reaction
- Particles gain more energy causing them to move faster
- This causes them to collide more frequently and with more energy each time increasing chances of exceeding activation energy
What does concentration/pressure refer to
How many particles there are per unit of volume
What state does concentration usually link to
Solutions/liquids
What state does pressure usually link to
Gases
If concentration/pressure is increased, how will this effect the rate of reaction
- more particles per unit of volume causes collisions to be more frequent increasing rate of reaction
If surface area is increased, how will this effect the rate of reaction
- increasing the surface area allows for more reactions to take place on it causing frequency of collisions to be higher
Which of these has the highest surface area: volume ratio
- Solid block
- Small Chunks
- Powder
Powder has the highest surface area: volume ratio and would increase frequency of collisions the most
If a catalyst is used, how will this effect the rate of reaction
- a catalyst will lower the activation energy increasing the frequency of successful collisions
What is a catalyst
A substance that speeds up a reaction without being used up in the reaction themselves
Draw and label a reaction profile
Graph:
Energy along y axis
Progress of reaction along x axis
Reactants line above products line
Curve attaching the product and reactant line
Activation energy (bit above top of line to reactants)
Overall activation energy (fully from reactants to products)
What are the most commonly used catalysts
Transition metals such as cobalt and nickel
Which 2 elements are most used as catalysts
Cobalt and nickel
What are we wanting to happen when increasing temperature, concentration/pressure, surface are and catalysts
We want a higher rate of reaction
