Reaction Rates Flashcards
Factors affecting reaction rate:
- Surface area of reactants
- Concentration of reactants
- Pressure of gases
- Temperature of system
- Catalysts
Rate of reaction:
Change in concentration of a reactant/product over a period of time.
Amount of substance produced /time taken
What is the collision theory:
For a collision to lead to a reaction, the reactants must:
- Collide with each other
- Collide with enough energy to break bonds in reactants
- Collide in correct orientation to break bonds and form new bonds.
What is activation energy:
The minimum energy required to form a reaction (Ea).
If the energy of the collision is equal to or greater than the activation energy, then the reaction will occur.
What is the transition state?
When the activation energy is absorbed, the reactant enters a state in-which it breaks bonds and forms new ones simultaneously, leading to a new arrangement of atoms.
Two main ways of increasing reaction rate:
- Increasing frequency of collisions
- Increasing frequency of collisions with an energy =/> than activation energy.
Changing concentration/pressure of reactants:
Increasing concentration of solution increases number of particles. This increases frequency of collisions which increases freq of successful collisions.
In gaseous phase, increasing the pressure is equivalent to increasing concentration.
Changing surface area of reactants:
Increasing the surface area of a substance allows for more collisions. More particles exposed so increase in reaction rate.
Changing the temperature of reactants:
As temp increases, KE increases, which means more freq of collisions = more successful collisions = increase in reaction rate.
What are the types of catalysts?
Homogenous Catalysts (Same physics state as reactant)
Heterogenous Catalysts
(Diff physical State as reactant)
What is a catalyst?
Is a substance that increases reaction rate by providing an alternate path of lower activation energy. It is not consumed in the process.
What does lower activation energy mean?
It means more particles have sufficient energy to react.
What are enzymes?
Are biological catalysts made of proteins that can produce faster reaction rates. They are more selective, can only catalyse some reactions.
They work by forming an enzyme-substrate complex.
Inorganic Enzymes?
Can be used to catalyse many reactions.
Catalytic Converters:
Designed to remove pollutant gases from engine ommisions, by converting them into non-toxic gases.
Reactants pass through a honeycomb structure usually made with a metal surface acting as a catalyst.
Is a heterogenous catalysis.
