Chapter 9 Flashcards
What are particles in liquids and gases always doing?
They are always moving and colliding with each other
What are the 2 conditions for a reaction to take place?
- They collide in the right direction. They need to be facing each other
- They must collide with enough energy
What is the collision theory?
The conditions for the reaction to occur.
What is the activation energy?
The minimum amount of kinetic energy particles need to react
Why do the particles need the activation energy for the reaction to start?
So the bonds can break
How do you give particles energy?
By heating them
What reaction will happen easier, reactions with low activation energies or reactions with high activation energies?
Reactions with low activation energies, as less energy is required
Do molecules all have the same amount of energy?
No
What does a Maxwell-Boltzmann Distribution show you
The amount of molecules which have the required activation energy
Why does a Maxwell-Boltzmann distribution start at (0,0)?
Because no molecules have 0 energy
What energy do molecules have to have in order to react?
> the activation energy
What does increasing the temperature do?
It increases the reaction rate
If you increase the temperature, what will the particles have more of on average?
More kinetic energy so will move faster
What will differ with a Maxwell-Boltzmann distribution when you increase the temperature?
More molecules will have the required activation energy
If molecules are flying about faster, what will they do more often?
They’ll collide more often
What does increasing the concentration do to the reaction rate?
It increases the reaction rate
Why does increasing the concentration increase the reaction rate?
More particles in a given volume, so particles will collide more frequently
What does increasing the pressure do to the reaction rate?
It increases the reaction rate
Why does increasing the pressure increase the reaction rate?
More particles in a given volume of gas, so more collisions
What does a catalyst do to the reaction rate?
It increases the reaction rate
What do catalysts do?
They lower the activation energy, by providing a different way for bonds to be broken and remade
What is the reaction rate?
The change in the amount of reactant or product per unit time
Why would you use a catalyst?
To increase the reaction rate
Do catalysts get used up in the reaction?
No
What is a heterogeneous catalyst?
One that is in a different phase from the reactants
In a reaction containing a heterogeneous catalyst, where does the reaction occur?
On the surface of the catalyst
What does increasing the surface area of the heterogeneous catalyst do?
It increases the rate of reaction, as there are more molecules that can react at the same time.
How does a heterogeneous catalyst work?
By lowering the activation energy of the reaction
What is adsorption?
When reactant molecules arrive at the surface and bond with the solid catalyst
What happens to the bonds between the reactant’s atoms during adsorption?
They are weakened and break up
How are radicals formed during adsorption?
The bonds between the reactant’s atoms are weakened and break up, which form atoms or molecules with unpaired electrons.
What do the radicals do once formed by adsorption?
They get together and form new molecules
What is desorption?
When the new molecules are detached from the catalyst
