Kinetics
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What does the collision theory state?
A reaction will not take place unless particles collide with energy equal to or greater than the activation energy
What is activation energy?
The minimum energy needed for a reaction to start
Why is activation energy needed?
To break bonds within reactant particles
What must happen for a reaction to occur?
Particles must collide with E>_ Ea
Why are most collisions unsuccessful?
Most particles don’t have E>_ Ea
What happens in an unsuccessful collision?
Particles bounce off each other and do not form products
What is a successful collision?
A collision where particles react to form products
Why might a reaction occur very slowly?
Only a small number of particles have E>_Ea
Why do some particles have very little energy?
Collisions cause some molecules to slow down or lose energy
Why do reactions with high Ea need heating?
To give particles extra energy
Why do reactions with low Ea happen easily?
Less energy is required for particles to react
What does a maxwell-boltzmann distribution show?
The range of kinetic energies of particles at a given temperature
How are particle energies distributed?
Some have low energy, some high, most are in between
What fraction of particles can react?
Only a small fraction have enough energy to overcome Ea
What is the rate of reaction?
Rate of change in concentration per unit time
Draw maxwell-boltzmann curve.
How does is change with different conditions
What are the units of rate of reaction?
moldm-3s-1
What factors affect rate of reaction?
Temperature, concentration, pressure, catalysts, surface area
How does increasing temperature increase rate?
More particles have E>_Ea and collisions are more frequent
How does increasing concentration increase rate?
More particles per unit volume so more frequent successful collisions
How does increasing pressure increase rate?
More particles per unit volume so more frequent successful collisions
How does a catalyst increase rate?
Lowers Ea so more particles have E>_Ea
How does increasing surface area increase rate?
More reactant particles available so more frequent collisions
What happens to the distribution curve at a higher temperature?
Moves right, becomes wider, peak lower and shaded area larger