Ch. 10 reaction rates and equlibrium
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rate of chemical reation
how fast a reactant is used or product is made
rate=
change in conc / time mol dm-3 s-1
explain the shape of a conc time graph
steep, ROR fastest at start, reactants at their highest conc slows down as they get used up levels out as one reactant is used up
what can change ROR
temp conc (pressure if reactants are gasses) catalyst SA of solid reactants
what makes a collision effective
particles collide in correct orientation with sufficient energy to overcome activation energy barrier
how can u follow and record the process of a reaction
monitor: removal (decrease in conc.) of reactant formation (increase in conc.) of a product if a reaction forms a gas you can . measure vol of gas produced . change in weight as gas released
what does a catalyst do
changes the ROR without undergoing any permanent changes itself not used up may form and intermediate with a reactant or provide a surface for a reaction to take place regenerated at the end of a reaction
how does a catalyst increase the ROR
provides an alternative reaction pathway of lower activation energy
homogeneous catalyst
same physical state as the reactant
heterogeneous catalyst
different physical state to the reactants usually solid with gaseous reactants
economic and sustainability importance of catalysis
reduces temp needed for reactions and energy consumption, so less fossil fuels burnt resulting in a faster cheaper more eco friendly industrial process
features of a Boltzmann distribution curve
no molecules have 0 energy area under curve = total no. molecules no maximum energy of a molecule, curve never reaches x axis
effect of increased temp on Boltzmann
peak flattens more molecules over or = Ea Ea stays in the same position
effect of catalyst on Boltzmann
Ea is lower Ec curve stays the same
equlibrium
rate of forward reaction = rate of reverse reaction conc of reactants and products do not change
why are equilibriums dynamic
the forward and reverse reaction are constantly happening
what is required for a reaction to stay in equilibrium
closed system temp, pressure, conc of reactants or products cant be affected by outside influences
le chateliers principle
when a system at equilibrium is subjected to an external change the system readjusts itself to minimise the effect of that change
conc change with equlibrium
more products formed - position of equilibrium shifts to the right more reactants formed - position of equilibrium shifts to the left
temp change with equlibrium
increase in temp - equilibrium shifts in endothermic direction AH+ decrease in temp - shifts equilibrium in the exothermic direction AH-
pressure change with equilibrium
pressure of a gas is proportional to its conc increase in pressure - equilibrium shift in direction of the side with fewer molecules, reducing pressure of system
catalyst with equilibrium
increases the rate at which an equilibrium is reached but does not effect the position of it it speeds the forward and reverse reaction up equally
endothermic reaction AH+ - increase in temp
eq moves right more products
endothermic reaction AH+ - decrease in temp
eq moves left more reactants