4 - Rates of Chem Reactions Flashcards
Collision theory
a theoretical model that explains the rates of chemical reactions in
terms of collisions between particles
rate of reaction
the change in concentration of a reactant or product over a period of time
proportion
the percentage of species with the necessary activation energy to react in a fixed sample
conditions for a reaction to occur
- Reactants must physically collide with each other.
- Reactants must collide with sufficient energy to break the bonds within them (activation energy, Ea).
- Reactants must collide with the correct orientation for bonds to actually break
affects of temp on reaction rate
reaction rate increases
reactants collide more frequently due to increased KE
- number of reactants with enough energy to
surpass the activation energy threshold increases, there will be a greater proportion
of successful collisions.
affects of SA on reaction rate
In the case of a solid reactant sample, when its
surface area increases, reactant particles can collide more frequently, resulting in
more successful collisions over a given period of time, and thus a faster reaction rate.
open system
a system in which both matter and energy can enter or leave
closed system
a system in which energy can enter or leave, but matter cannot
what are the ways in which rate of reaction can be measured
temp,
Change in mass due
to solid formation or
gas evolved
precipitate formation
colour change
volume of gas evolved
pH
function of catalyst
Catalysts interact and bind with reactants to provide an alternate reaction pathway
with a lower activation energy.
they do not increase the percentage yield of reactions
Heterogeneous catalysts
are those present in a different
physical state (or phase) to the reactants and products.3
Homogeneous catalysts
are those present in the
same physical state as the reactants and products
