Kinetics Flashcards
What is rate of reaction ?
The change of concentration of a reaction( or products) per unit of time.
What is activation energy ?
Minimum amount of energy required for particle to collide and for a reaction to begin.
Draw an energy profile graph
Notes
What is an exothermix reaction.
Reactants more energy than products.
What is an endothermic reaction ?
When products have more energy than reactants.
What factors affect rate of reaction ?
Temperature Concentration Pressure Surface area Catalyst
What is collision theory ?
Particles must collide
Particles must have sufficient (activation) energy
Particles must collide with correct orientation.
Why does a reaction not always occur even when particles collide ?
There may be insufficient energy or an incorrect orientation.
How does temperature affect rate of reaction and why ??
When temperature increases, particles gain more kinetic energy and number of particle collisions per second increases. Higher number of successful collisions. OR new particles have he activation energy so a higher proportion of collisions are successful.
How does concentration affect rate of reaction ??
Proportion of successful collisions is the same however there are more particles in the same volume so they collide more frequently and more successful collisions occur.
How does pressure affect rate of reaction ?
Same quantity of particles but in smaller volume therefore although the proportion of successful reactions remains the same, the particles collide more frequently. So a higher rate of successful collisions.
How does surface area affect rate of reaction?
More particles are able to collide with particles on the other reactant. Therefore there are more total collisions and more likely successful collisions. Proportion of collisions doesn’t change.
How does a catalyst affect rate of reaction ?
Decreases activation energy by providing an alternative reaction pathway where less energy is required.
Explain the Maxwell Boltzmann distribution ?
In any mixture of moving molecules the speed of particles will vary a great deal; very slow particles with low energy to very fast particles with Hight energy. However, most particles are close to the average speed.
Draw and label a Maxwell Boltzmann distribution.
In notes
How can you change kinetic energy of the Maxwell Boltzmann distribution?
Increases temperature: activation energy remains the same, most probable and average energy increases. Therefore more particles with activation energy.
Decrease temperature: activation energy remains the same. Most probable and average energy decrease. Fewer particles with activation energy.
Draw graphs showing how an increase or decrease in temperature affects a Maxwell boltzmann curve.
In notes
Draw how adding a catalyst alters a Maxwell Boltzmann distribution.
Notes
Lowers activation energy
What are the 2 catalyst types ??
Heterogenous
Homogenous
What is a heterogenous catalyst ??
A catalyst in a different phase to (E.g the reactant.
Solid catalyst and liquid reactant)
Give an example of what a heterogenous catalyst is used for
To convert toxic gases in exhausts to Carbon dioxide and water vapour which are less harmful.
What are homogeneous catalysts ?
A catalyst in the same phase as the reactant
E.g - both liquids
Give an example of what a homogenous catalyst is used for ?
Chlorine free radicals depleting the ozone layer
What are the advantages of catalysts ?
Lowers activation energy therefore making a reaction more economically efficient.
Lowers production costs.
Lowers energy demands meanning less carbon dioxide is produced so less environmental impact.
Not chemically changes so can be reused.
