Kinetics Flashcards
What does the collision theory state?
For a chemical reaction to take place, particles need to collide with each other in the correct orientation and with enough energy
This theory is fundamental in understanding how reactions occur at the molecular level.
What is an ineffective collision?
When particles collide in the wrong orientation or do not have enough energy and bounce off each other without causing a chemical reaction
Ineffective collisions do not lead to product formation.
What is collision frequency?
The number of collisions per unit time
Increasing collision frequency can lead to a higher rate of reaction.
How does an increase in collision frequency affect the rate of reaction?
It increases the number of particles with energy greater than the activation energy (Ea)
More effective collisions lead to faster reactions.
What is activation energy (Ea)?
The minimum amount of energy required for reactant particles to undergo a chemical reaction
The concept of Ea is crucial for understanding reaction rates.
In exothermic reactions, how do the energy levels of reactants and products compare?
The reactants are higher in energy than the products
This energy difference is key to understanding energy profiles in exothermic reactions.
In endothermic reactions, how do the energy levels of reactants and products compare?
The reactants are lower in energy than the products
This indicates that energy must be absorbed for the reaction to proceed.
How does the activation energy of endothermic reactions compare to that of exothermic reactions?
The Ea in endothermic reactions is relatively larger than in exothermic reactions
This reflects the greater energy requirement for endothermic processes.
What is required for a collision to be effective?
Reactant particles must collide in the correct orientation AND possess a minimum energy equal to the activation energy (Ea) of that reaction
Effective collisions are essential for product formation.
What is a catalyst?
A substance that increases the rate of reaction without taking part in the chemical reaction
Catalysts work by providing an alternative pathway with a lower activation energy.
How does a catalyst affect activation energy?
It provides an alternative pathway which has a lower activation energy
This allows reactions to occur more easily and quickly.
define rate of reaction
change in concentration of a substance over time.
how does concentration affect rate of reaction?
if it is concentrated there are more particles in a given volume and so more frequent collisions thus there’s more chance particles will E is greater than/or equal to Ea
how does pressure affect rate of reaction?
higher pressure particles are closer together so more frequent collisions thus there’s more chance particles will have E is greater than /or equal to Ea
how does temperature affect rate of reaction?
-higher temp means the particles are moving faster so collide more frequently
-higher number of collisions means higher number of successful collisions in the same amount of time
-higher temperatures means a higher proportion of the molecules have the Ea or more meaning a higher proportion of collisions is successful
-many more particles have E greater than or equal to Ea
how does pressure affect rate of reaction?
increasing surface area increases number of particles of reactant available to react and thus there will be more frequent collisions between the reactants. This leads to a higher chance of having E greater than or equal to Ea
What is a maxwell Boltzmann distribution curve?
A graph that shows the distribution of energies at a certain temperature
What happens when the temperature of a reaction mixture is increased?
-particles move around faster resulting in more frequent collisions
-proportion of successful collisions increases so more losses a higher activation energy
With higher temperatures the Boltzmann distribution curve flattens and the peak shifts to the right
Why does increasing temperature increase rate of reaction?
More effective collisions as particles have more kinetic energy making them move around faster
A greater proportion of the molecules having Ek greater than Ea
How do catalysts work ?
Increase the rate of reaction by providing the reactants with an alternative reaction pathway which is lower in activation energy
Two types of catalysts
Homogeneous and heterogeneous
What is a homogeneous catalyst?
The catalyst us in the same phase as the reactants
What is a heterogenous catalyst?
The catalysts is in a different phase to the reactants
What happens when catalysts lower Ea?
A greater proportion of molecules in the reaction have the Ea and thus have sufficient energy for an effective collision . As a result,rate of the catalysed reaction is increased compared to the uncatalysed reaction
