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Reaction Rate (Collision Theory (explains why (different reaction occur at…
Reaction Rate
Collision Theory
explains why
different reaction occur at different rates
suggests ways to change rate of reaction
Collision of molecules
must occur
for reaction to occur
collisions with enough energy
energy
increase temperature
particles have more energy
more likely to collide
correctly orientated
part of
concentration
more molecules present
more collisions
Activation Energy
minimum amount of energy reactants must have
to undergo a reaction
barrier between reactants and products
not enough energy
no reaction
collide and bounce apart
still reactants
enough energy
reaction occurs
higher activation energy
slower reaction rate
increase temperature
why affect reaction rate
energy level of molecules increase
reaction rate faster
frequency and force of collision increase
Factors Affecting
Temperature
increase in temperature
keeps activation energy same
increase particle kinetic energy
from absorbed heat
more molecules with higher energy
collide easier
rate of reaction increases
Surface Area
Heterogenous reactions
rate of reaction increase
if stirred
faster reaction
increase surface area
more contact from solution
expose more solid particles to liquid
liquid can bump into solid on surface of solid only
example
removal of harmful pollutants
catalytic exhausts
modern motor cars
such as
carbon monoxide
nitrogen oxides
unburnt fuel
Concentration of reactants
Increase reactant concentration
number of molecules with energy increase
increase reaction rate
more collisions occurring
directly proportional to reaction rate
Catalysts
increase reaction rate
lower activation energy
no change to them
heterogenous catalyst
reactant particles absorb to them
break or weaken bonds
example
biological
enzymes
Molecular Orientation
molecules need to collide with correct orientation
proper atoms line up with each other
bonds can break and reform
if not
bounce off each other
liquids and gases
constantly moving
high probability effective collision will occur
more complex molecules
fewer effective collsions
definitions
reaction rate
rate of change of concentration over time
rate at which reactant used up
length of reaction
effective collision
chemical bonds broken
products forms
ineffective collision
no product formation