KINETICS AND COLLISION THEORY Flashcards
according to the collision theory, a reaction can only take place if:
when particles have sufficient energy
when particles collide in the correct orientation (direction)
how can you achieve a fast reaction rate
plenty of rapidly moving particles in a small volume
why do most collisions between particles not lead to a reaction
dont have sufficient energy
incorrect orientation
what is activation energy
minimum amount of energy needed for a reaction to occur
describe the energy profile for an exothermic reaction
energy of the products is lower than the energy of the reactants
energy change is negative as energy is released from the reaction into the surroundings
describe the energy profile for an exothermic reaction
energy of the products is higher than the energy of the reactants
energy change is positive a energy is absorbed from the surroundings into the reaction
how can you provide extra energy to particles
heat
what does the maxwell boltzmann distribution show
spread of energies that molecules of a gas have at a particular temperature
which particles can react
particles with energy greater than the activation energy
what factors can effect the rate of a reaction
concentration
pressure
temp
surface area
catalyst
what are catalysts
speeds up the rate of reaction without being used up
how do catalysts increase the rate of reaction
providing an alternate reaction pathway
which has a lower activation energy
what happens to the amount of energy particles have when a catalyst is introduced
stays the sameq
how does increasing temperature affect rate
increasing the temp of a gas will increase the kinetic energy of molecules
means many more particles have energy greater than the activation energy
so more frequent successful collisions
how does increasing temp effect MBD
peak is lower and moves to the right
most probable energy will increase as it is more shifted to the right
number of particles with very high energy increases
total area under the curve remains the same
number of particles doesn’t change
why does a small increase in temperature lead to a great difference in rate of reaction
many more molecules with energy equal to or greater than activation energy
large increase in number of successful collisions per unit time
how does concentration affect rate
increase in concentration means more particles in a fixed volume
particles are closer together
so more frequent successful collisions
how does pressure effect rate
increasing pressure means more particles in a fixed volume
so particles are closer together
more frequent and successful collisions
how does surface area effect rate
smaller p[articles have a higher SA:V
more particles exposed to other reactant
so more frequent successful collisions
how can we increase surface area
crush into powder
cut into smaller pieces
add holes / ridges
what happens at the start of a reaction
reaction is fast as there is more frequent collisions
what happens to rate as conc of reactant particles decreases
slows down
when does a reaction end
when all of one reactant is used up
