Kinetics Flashcards
Reaction Rate
The change in concentration (or amount) of a reactant or product over time
Formula for Rate of Reaction
Amount of reactant used or product formed -:- Time
A reaction will only take place between two particles if…
They collide in the right direction.
They need to be facing each other in the right way
They collide with at least a certain minimum amount of kinetic (movement) energy
Activation Energy
The minimum amount of energy that particles need to react
Area under a Maxwell-Boltzmann Distribution
Equal to the total number of molecules
Why does the curve start at (0,0) in a Maxwell-Boltzmann distribution curve?
Because no molecules have zero energy
The peak of a Maxwell-Boltzmann Distribution curve
Represents the most likely energy of any single molecule
Where is the mean (average) energy of all the molecules on a Maxwell-Boltzmann Distribution curve?
A bit to the right of the peak of the curve
Which molecules can react on a Maxwell-Boltzmann Distribution curve?
The few molecules that have more than the activation energy
Increasing the temperature of a reaction
Effect on Maxwell-Boltzmann Distribution Curve
If you increase the temperature of a reaction, the particles will on average have more kinetic energy and will move faster.
A greater proportion will of molecules will have at least the activation energy and be able to react, changing the shape of the Maxwell-Boltzmann distribution curve- pushing it over to the right
Speed of molecules and higher temperature
At higher temperatures, because the molecules are flying about faster, they’ll collide more often
Why can quite small increases in temperature lead to quite large increases in reaction rate?
With increase in temperature you get more collisions and more energetic collision occurring
Increasing concentration of a reaction
If you increase the concentration of reactants in a solution, the particles will on average be closer together.
If they’re closer, they’ll collide more often. If collisions occur more frequently, they’ll have more chances to react.
This is why increasing concentration increases reaction rate
Increasing pressure of a reaction
If a reaction involves gases, increasing the pressure works just as increasing the concentration.
Raising the pressure pushes all of the gas particles closer together, making them more likely to collide.
So collisions take place more frequently and the reaction rate increases
Catalyst
A catalyst is a substance that increases the rate of a reaction by providing an alternative reaction pathway with a lower activation energy.
The catalyst remains chemically unchanged at the end of the reaction
