9. Kinetics I
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Give the conditions for a chemical reaction to occur by collision theory
-Particles collide - collide in the right direction/orientation - collide with the minimum activation energy
Define activation energy
The minimum energy which particles need to collide and start a reaction
Describe the maxwell Boltzmann distribution graph
starts at 0 as no particles have no energy Y axis - number of particles with this energy X axis - Energy
How does increasing temperature affect rate of reaction
increases rate Increasing temperature will increase the rate of reaction. Particles collide more frequently which increases the number of successful collisions. Particles collide with more energy which increases the proportion of successful collisions. More particles collide with E≥Ea.
Describe how the maxwell boltzmann distribution graph would change with increased temperature and decreased temperature
Higher temperature: Peak sits to the right Peak is lower Area under the curve remains the same Area under curve beyond activation energy increases Lower temperature: Peak sits to the left Peak is higher Area under curve remains the same Area under the curve beyond activation energy decreases (opposite is true for lower temperature)
Describe how increasing concentration impacts rate
More particles in a given volume so particles collide more frequently so there are a greater number of successful collisions with the minimum activation energy HOWEVER, proportion of successful collisions is unchanged
Describe how increasing surface area impacts rate
Reactant particles collide more frequently so there are a greater number of successful collisions that collide with the minimum activation energy. However, proportion of successful collisions is unaffected.
Explain how a catalyst works
A catalyst speeds up the rate of reaction without being used up by providing an alternate reaction pathway with a lower activation energy.
Define heterogenous catalyst
Catalyst is in a different physical state to the reactants. Eg: its a solid and all other reactants are gasses. –> these solid catalysts provide a surface for the reaction when all reactants are gasses
Describe how heterogenous catalyst provide a surface for a reaction (how do they work)
Reactants adsorb on to the surface of the catalyst at active sites. Reaction takes place which weakens bonds Product is desorbed
Define homogenous catalyst
Catalyst is in the same physical state to other reactants
Give the 2 benefits of using a catalyst
–> Catalysts speeds up the rate allowing lower temperature to be used, hence lower energy costs –> Saves time