1.5 Kinetics
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What is the collision theory?
The particles of the reactants need to collide having frequent successful collisions above the activation energy
What is rate of reaction?
Frequency of collisions of the reactant particles at or above the activation energy Resulting in a change in concentration of products or reactants over a given period of time
What must happen in order for a successful chemical reaction to take place?
Particles must: Collide Collide with enough energy Collide with the correct orientation
The is the activation energy?
The minimum amount of energy particles must have to start a reaction
What factors affect rate of reaction?
Temperature* Concentration Surface area Catalysts
How does temperature affect the rate of reaction?
It gives the particles more kinetic energy. The vibrate and move more at a greater force causing more frequent collisions above the activation energy. Increasing the rate of reaction
How does concentration affect the rate of reaction?
Higher concentration means there are more particles in a given volume therefore more opportunities for successful frequent collisions. This will increase the rate of reaction
How does surface area affect the rate of reaction?
A higher surface area means there are more particles exposed to the acid so there are more successful frequent collisions above the activation energy. This will increase the rate of reaction
Which has a higher surface area? Marble chips or Marble powder
Marble powder
What does a catalyst do?
It lowers the activation energy By providing an alternative reaction pathway Allowing more successful frequent collisions above the activation energy
What is a catalyst?
It speeds up a chemical reaction and doesn’t get used up
Are catalysts used up in a reaction? How can you tell?
No, they have the same mass at the start and end of the reaction
Are catalysts costly? Economical?
Expensive but economical as they don’t need replacing often
Why are catalysts important in industrial processes?
To reduce the energy which will reduce the costs and environmental impact
How can we link temperature to rate of reaction?
For every 10 degree increase the rate of reaction approximately doubles
What graphs can we use to show rates of reactions?
Maxwell-Boltzmann Distributions
What are the labels on the Maxwell-Boltzmann Distribution graphs?
Number of particles - up the side Energy- along the bottom
What does the Maxwell-Boltzmann curve look like?
Very steep initially Gradual decline =asymmetrical
What is the highest peak on the Maxwell-Boltzmann curve?
The most probable energy a particle will have as it is the most frequent i.e mode
What are some factors of the Maxwell-Boltzmann curve?
The area under the curve represents the total number of particles in the sample The curve starts at the origin The curve never touches the bottom x axis again = asymptote
Why does the Maxwell-Boltzmann curve never touch the x axis after the start?
That would imply the particles have a finite amount of energy but particles have the potential for an infinite amount of energy