Topic 9: Kinetics I Flashcards
What are the assumptions of the simple collision theory?
Particles are colliding with at least the minimum activation energy and are colliding with the correct orientation
What factors affect rate of reaction?
concentration of regents, pressure, surface area, presence of catalyst, temperature
What is activation energy?
The minimum energy required for a reaction to occur when particles collide
Why can an exothermic reaction continue?
Once it starts, it releases enough heat energy for the reaction to continue
Explain how concentration affects the rate of reaction
As concentration increases, there is an increased number of particles (specific) per unit volume and hence there are more successful collisions per unit time so the rate of reaction increases
Explain how temperature affects the rate of reaction
An increase in temperature increases the rate of reaction. It leads to an increase in kinetic energy of the particles. As the particles move faster, there is an increased frequency of collisions per second. More particles also have at least the minimum activation energy are more collisions are successful
Explain how surface area affects the rate of reaction
An increase in surface area increases the rate of reaction. There is an increased number of particles available to collide and so an increased frequency of collisions per unit time
What do Boltzmannn distribution curves show
The number of particles with a particular amount of kinetic energy in a gaseous sample. This explains why only a small proportion of molecules have sufficient energy to react
Draw a Maxwell-Boltzmann curve of distibution
Symmetrical then gradient decreases (doesn’t touch 0)
Activation energy
No of particles on y axis
Energy on y axis
What does the area under the curve represent (Boltzmann)
The total number of particles
How does temperature affect the Boltzmann distribution
The peak shifts lower and to the right. T+t. The line plateaus at a higher number of particles. There is a greater proportion of molecules that have the activation energy
How does a catalyst affect the Boltzmann distribution
The Ea shifts to the left. A greater proportion of particles have the activation energy
Draw the reaction profile of a catalysed reaction
Dip represents the formation of an intermediate which is less stable and so is higher in energy that the reactants and products
What does a catalyst do
It provides an alternative reaction pathway with a lower activation energy
Homozygous catalyst
The catalyst and reactants are in the same physical state eg acid
