3.1.5 Kinetics Flashcards
(16 cards)
define collision theory
reactions can only occur when collisions take place between partciles having sufficient energy (activation energy).
define activation energy
the minimum energy which particles need to collide to start a reaction.
draw out the Maxwell Boltzmann curve
go through origin
never meet x axis
labelled Ea, Emp and mean energy of particles
energy on x axis
number of molecules on y axis
where can the most probable energy (Emp) be found on the curve
the peak
where is the mean energy of particles found on the curve and why
right of the peak
it accounts for particles with higher energies in the tail of the distribution
how can a reaction go to completion if few particles have energy greater than Ea
particles gain energy through collisions
what happens to the distrubution when temperature increases and draw it out
the curve shifts to the right more molecules with higher energy
the curve becomes broader and flatter
more particles with a wider range of energies
what happens to the distrubution at lower temperatures
peak shifts towards the left
curve becomes narrower and taller
fewer particles have higher energies
define rate of reaction
chnage of concentration of a substance in unit time
how to calculate rate of reaction with a graph
gradient of tangent to curve
what happens to the reaction at high concentrations and pressure
more peartcles per unit volume
greater frequency of collisions
high freqency of successful collisions
how does higher concentrations impact the distrubution curve
the shape of curve will not change
so Emp and mean energy won’t change
BUT curve is higher and greater area under
as there are more particles
explain the effect of increasing temperature of reaction
energy of particles increases
frequency of collisions increases
particles will collide MORE OFTEN with energy greater than the activation energy
explain the effect of increasing surface ares in a reaction
higher frequency of collisions
higher frequency of succesfull collisions
increases rate of reaction
define a catalyst
A substance that increases the rate of a chemical reaction by providing an alternative reaction pathway with a lower activation energy. It is not used up in reactions
how does a catalyst effect the reaction rate
lower activation energy
more particles have energy above the activation energy
higher frequency of successful collisions
reaction is now faster
