1.5 - Kinetics Flashcards
What is the ‘collision theory’?
Collision theory says that a reaction won’t take place between two particles unless they collide in the right direction and they collide with at least a certain minimum amount of kinetic energy
What is ‘activation energy’?
Activation energy is the minimum amount of kinetic energy particles need to react
What is on the x-axis and y-axis of a Maxwell-Boltzmann distribution graph?
y-axis = number of molecules x-axis = kinetic energy
Where does the curve start on a Maxwell-Boltzmann distribution graph?
The curve starts at the origin because no molecules have 0 energy
Where is the average energy on a Maxwell-Boltzmann distribution graph?
The average energy of all of the molecules is a little bit right of the peak
What does the area under the curve equal to in a Maxwell-Boltzmann distribution graph?
The total number of molecules
How does temperature affect the rate of reaction?
If you increase the temperature of a gas, the molecules will on average have more kinetic energy and will move faster. Also, as the molecules are flying faster, they’ll collide more often. These factors lead to an increase in the rate of reaction
How does temperature affect a Maxwell-Boltzmann distribution graph?
The peak is lower and is shifted to the right - the area under the curve must be the same as the total number of molecules hasn’t changed
How does the concentration affect the rate of reaction?
If you increase the concentration of reactants in a solution, the particles will on average be closer together. This means collisions are more frequent and therefore more likely to react
How does pressure affect the rate of reaction?
In gases, the pressure affects the rate of reaction in the same way that concentration does; the particles will be closer together and are therefore more likely to react
How does concentration affect a Maxwell-Boltzmann distribution graph?
The shape of the curve will be the same, but with the whole graph higher as there are more particles
What are catalysts used for?
Catalysts are used to make a chemical reaction happen faster. A catalyst increases the rate of reaction by providing an alternative reaction pathway with a lower activation energy. The catalyst is chemically unchanged at the end of the reaction
How does a catalyst affect the Maxwell-Boltzmann distribution graph?
The curve stays exactly the same, but the activation energy moves to the left, meaning there are more particles with the activation energy
What is the rate of reaction?
The rate of reaction is the change in the amount of reactant or product over time
How can the rate of reaction be calculated?
If a precipitate forms, the solution becomes cloudy and therefore you can time the time taken for a cross to disappear
If the product is a gas, the change in mass on a balance can be calculated
A gas syringe can be used to collect gas
