Kinetics Flashcards
What is activation energy?
The minimum energy needed for a reaction to occur
What is a catalyst?
A substance that speeds up a chemical reaction but is chemically unchanged at the end. They work by providing an alternate reaction pathway with a lower activation energy
What is enthalpy change?
A heat change at constant pressure
What is the rate of a reaction?
Change in the concentration of a reactant (or product) per unit time
How do you calculate the rate of reaction?
Amount of product/ Time
What are 3 methods for measuring the rate of reaction?
- measuring a decrease in mass
- measuring the volume of gas given off
- timing how long it takes for a precipitate to form
What does collision theory state?
For a reaction to occur, particles must:
-Collide with each other
-Have the correct orientation
-Have sufficient energy to react (activation energy)
What 3 things can cause the rate of reaction to increase?
-Increase the frequency of collisions
-Increase energy of reactants
-Lower the activation energy using a catalyst
How do you increase the rate of reaction?
-Increasing the concentration
-Increase the surface area
- Increase temperature
- Add a catalyst
-Increasing the pressure
How does increasing the concentration/pressure increase the rate of reaction?
-Increases the number of reactant molecules per unit volume of a solution
-Increases the frequency of collisions
How does increasing the surface area increase the rate of reaction?
- More reactant is exposed
- More successful collisions
How does increasing the temperature increase the rate of reaction?
- Increases the kinetic energy of reactant molecules
- More have sufficient energy to react and so there are more successful collisions
How does adding a catalyst increase the rate of reaction?
- Lowers activation energy
- More particles have sufficient energy to react
What does a Maxwell- Boltzmann distribution curve look like?
What does the starting point of a Maxwell- Boltzmann distribution curve show?
Only very few reactant molecules have a low amount of energy
What does the end of a Maxwell- Boltzmann distribution curve show?
Only very few reactant molecules have a high amount of energy
Where does the modal/ most probable amount of energy lie on a Maxwell- Boltzmann distribution curve?
At the very peak of the curve
Where does the mean average particles with energy lie on a Maxwell- Boltzmann distribution curve?
Just below the peak of the curve
What does the area under a Maxwell- Boltzmann distribution curve show?
The total number of reactant particles
Does the Maxwell-Boltzmann distribution curve ever touch the x axis and why/why not?
NO because we can’t say theres a maximum amount of energy particles have as it goes to infinite
Which part of a Maxwell- Boltzmann distribution curve shows the particles that have sufficient energy to react?
Area shaded in purple
What are you increasing if you increase the concentration in a reaction?
Increasing the number of particles present
What happens to a Maxwell- Boltzmann distribution curve if you increase the concentration?
The curve shifts upwards as area is increased due to increased number of particles
What stays the same although the concentration is increased in a reaction?
The proportion of molecules that can react