Studied by 0 people
Rate of reaction
Change in concentration of a reactant or product in a given time
Rates of reaction are affected by?
Concentration
Temperature
Surface area
Particle size
Catalyst
Define Collision theory
Reactions occur when reactant particles collide provided that they collide with a certain minimum kinetic energy, the activation energy
Does orientation matter
Yes, particles must collide with the correct orientation for a reaction to take place
What are some ways catalysts can interact with a reaction
May react to form an intermediate
It is later regenerated
What does a catalyst do
A catalyst lowers the activation energy of a reaction by providing an alternative route for the reaction with lower activation energy
Define a Heterogeneous catalyst
A catalyst that is in a different physical state to the reactants
Define a Homogeneous catalyst
The catalyst and reactant are in the same physical state
How does a heterogeneous catalyst work?
reactants absorbed onto surface of the catalyst and the reaction takes place then the products that are formed de absorb and diffuse away
What is the Boltzmann distribution
shows the no. of molecules with a particular energy, at one temp, often shown as a graph
Important features of the Boltzmann graph
Area under the curve = total no. of molecules
• No molecules have ZERO energy (curve starts at origin or 0,0)
• No MAXIMUM energy (curve not get to 0 on x-axis)
• ONLY molecules with energy greater than Ea can react
How would a catalyst effect the Boltzmann distribution
The Ea is lowered so a greater number of particles have greater energy than the Ea so an increased rate of reaction
Define Dynamic equilibrium
dynamic equilibrium is the equilibrium in a closed system when the rate of forward reaction = rate of reverse reaction
What are the characteristics of dynamic equilibrium
The concentrations of the reactants and products
do not change over time.
– rate of forward reaction = rate of reverse reaction
Le Chatelier’s principle
• When a system in dynamic equilibrium is subjected to change, the position of equilibrium will shift to minimise the change.
• Can alter position of equilibrium by changing: – Concs, pressure (gases) or temp
What are the effects of altering concentrations on equilibrium
Increasing concn of reactants causes ≡m to move to product side.
Increasing concn of products causes ≡m to move to reactants side.
Decreasing concn of reactants causes ≡m to move to reactant side.
Decreasing concn of products causes ≡m to move to product side.
What are the effects of pressure on equilibrium
Low pressure it moves towards the side with the most number of moles
High pressure it moves to the side with least number of moles
Effect of temperature on equilibrium
Increase in temperature leads to equilibrium shifting to the lhs as it favours the endothermic reaction
Decreasing the temperature will lead to equilibrium shifting to the rhs as it favours the exothermic reaction
