TOPIC 9:Kinetics 1 Flashcards
(13 cards)
Rate of reaction
Change of concentration or amount/time
Amount of reactant used or product made/time
Collision theory
For reaction to occur collision must be
In right direction and with right amount of kinetic energy
Activation energy
Minimum amount of energy required for a reaction to occur
Maxwell-Boltzmann Distribution
Shows energy in gas particles
Area under graph =number of gas molecules
Peak = most likely energy in a sample
Right = mean energy
Right of all = activation energy
Effects on rate
Increasing temperature- increases, curve shifts to right, peak is lower, area unchanged, area beyond aE is bigger. (Faster and more successful collisions)
Increasing Pressure and concentration -increase
Catalysts increases, provides an alternative pathway (lower aE)
Catalysts
Chemically unchanged after reaction and speed up the reaction (eg zeolite)
Alternative pathway lowering aE
Heterogeneous catalyst
(different state/phase)
increasing its surface area will increase the rate
Adsorption: bond with surface of solid catalyst
Bonds weaken to form radicals which react with each other to form new substances
Desorption: new molecules released from surface
Homogeneous catalysts
(same phase/state usually aq)
Form an intermediate species by combining with reactant to react and form product, then get reformed
So two bumps in energy profile for intermediate to form
Eg. Sulphuric acid to make an ester
Example of a heterogeneous catalyst
Haber process:
N2(g) + 3H2(g) -> 2NH3(g)
Solid iron catalyst used
Why use a catalyst
- lower temperature and pressure (less energy and CO2)
- speed up
- change in properties
- less waste produced
Catalytic converter
Platinum
2CO + 2NO -> 2CO2 + N2
Rate measurement
- cross disappeared over time (error)
- amount of mass loss of gas lost (fume cupboard if toxic)
- volume of gas produced with gas syringe over time
Rate from graph
Volume over time
= Gradient
Tangent if curve (specific point)
Initial, tangent at t=0
