3.2.2 Reaction rates & 3.2.3 Equilibrium Flashcards
collision theory
minimium amout of energy between them and they must collide with the correct orientation for reaction to occur
rate of reaction definition and units
rate at which reactants are converted into products
mol dm-3 s-1
activation energy
minimium amount of energy required to start the reaction by the breaking of bonds
rate equation
change in concentration / time
factors affecting rate
concentration
temperature
surface area
catalyst
pressure
how does increasing concentration affect rate
more particles present per unit volume so particles collide more frequently
how does increasing temperature affect rate
particles have more kinetic energy so they collide more with more energy so a greater proportion of collisions have energy greater than the activation energy
how does increasing surface area affect rate
more particles are exposed for collisions and so they collide more frequently
how does a catalyst affect rate
provides alternative reaction pathway with a lower activation energy so a greater proportion of the collisions have energy greater than the activation energy
how does increasing pressure of gas affect rate
more particles present per unit volume so particles collide more frequently
homogenous catalyst
catalyst is the same state as reactants
heterogenous catalyst
catalyst is a different state to reactants
benefits of a catalyst in terms of money and sustainability
catalyst provides alternative pathway with lower activation energy so reduces temp required so less electricity and fuel used so increase profitibility
uses less fossil fuels so reduces emmission of CO2 linked to global warming so increase sustainability
features of the Boltzmanns distrubution
no molecules have zero energy
area under the curve is equal to the total number of molecules
theres no maximium energy for a molecule as curve does not meet x axis at high energy
methods for following progress of chemical reactions
monitor removal of reactant or formation of product
method for monitoring reaction producing gas
monitor volume of gas produced using gas cylinder at certain intervals or in a specific time
monitor loss of mass of reactants using mass balance
what happens to the boltzmanns distrubution if you increase the temperature
graph will strech over greater range of energy values as more molecules will have a higher energy
what happens to the area under the curve of the boltzemanns distrubution if you increase the temperature
stays the same
Factors affecting equilibrium
concentration
catalyst
pressure
temperature
how does increasing the concentration of N2 affect how ammonia is produced
(3H2 +N2 <-> 2NH3)
forward reaction is favoured as theres more reactants so they want to use them up
how does increasing the pressure affect how ammonia is produced
(3H2 +N2 <-> 2NH3)
favours forward reaction as it moves to the side with fewer moleules to minimise the increase in pressure
how does increasing the temperature affect how ammonia is produced
(3H2 +N2 <-> 2NH3)
-exothermic reaction
favours backwards reaction as its endothermic direction so takes the energy in
how does adding a catalyst affect how ammonia is produced
(3H2 +N2 <-> 2NH3)
affects both forward and backwards reaction but equilibrium will be reached faster
Le Chatelier’s principle
if system at equilibrium is disturebed by changing the conditions the position of equilibrium moves in the direction that counteracts the change
conditions of an equilibrium system
rate of forward reaction = rate of reverse reaction
concentration of products and reactants doesn’t change
must be in a closed system
Kc
[products] / [reactants]
what do the [ ] mean
concentration
N2 + O2 <-> 2NO
Kc equation
[NO]^2/ [N2][O2]
what position is equilibrium if Kc> 1
towards the products so forwards reaction
what position is equilibrium if Kc<1
equilibrium is towards the reactants
what position is equilibrium if Kc=1
equilibrium is halfway between reactants and products
