Kinetics Flashcards
What is kinetics?
The study of how quickly chemical reactions occur
What needs to happen for a reaction to occur?
The reactant particles must collide, and the collision must have sufficient energy so that bonds can be broken and in the correct orientation
What is the activation energy of a reaction?
The minimum energy required for a reaction to occur
How is energy distributed in a sample of gas or liquid?
Energy is passed from molecule to another when they collide and the collisions are elastic (no energy loss).
Describe the important features of a Maxwell-Boltzmann graph:
No particles have zero energy (so goes through the origin)
Only a few particles have very high energy
There is no maximum energy
Where is the most probable energy and average energy found on the Maxwell-Boltzmann graph?
Emp- top of peak
Eav- to the right of Emp
What is the rate of reaction as shown in a graph?
The gradient of the graph, when concentration is plotted against time
Define rate of reaction:
Change in concentration of a substance in unit time
What is rate of reaction affected by?
Concentration of reagents in solution or the pressure of gaseous reagents
Surface area of any solid reagent
Temperature
Presence of a catalyst
How does concentration/pressure affect the rate of reaction?
An increase in the concentration increases the number of ions/molecules per cm^3. This increases the frequency of collisions between reactants and so increases the frequency of effective collisions and therefore the rate.
How does surface area of any solid reagent affect the rate?
Increasing the surface area increases the frequency of collisions between reactants and so increases the frequency of effective collisions and therefore the rate of collisions
How does temperature affect the rate of reaction?
An increase in temperature increases the energy of molecules so they move faster and collide more frequently and with greater energy. A small increase in temperature greatly increases the number of molecules with energy greater than the activation energy, therefore the proportion of collisions that are effective increases and there is a large increase in rate.
How does the presence of a catalyst affect the rate of a reaction?
A catalyst increases the rate of reaction and is chemically unchanged at the end of the reaction
The catalyst increases the rate of a reaction by providing an alternative route with a lower activation energy
