6+16: kinetics Flashcards
for 0 order, the rate of the reaction is _____________ of [rxt]
independent
which order of reaction is the rate directly proportional to [rxt]?
1st order
for 2nd order, rate is directly proportional to…
[A]2
draw the conc - time graph for 0 order
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draw the conc - time graph for 1st order
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draw the rate - conc graph for 2nd order
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draw the rate - conc graph for 0 order
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draw the rate - conc graph for 1st order
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draw the conc - time graph for 2nd order
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what is the equation for half-life
t1/2 = ln2/k
t1/2=lnk can only be used for _______ order reactions
1st
what is the equation used to find the number of half lives for 1st order reactions?
Ct/Co = (1/2)^n
Ct – [ ] at time t
Co – initial [ ]
n – no. of half lives
what methods can be used to measure the volume of gas produced?
- gas syringe
- water displacement method
how can changes in mass be measured?
with an electronic balance
if a reactant is iodine, what chemical method of analysis can be used?
clock reaction
what does quenching mean?
it means stopping the rxn
why must quenching be done in titration?
quenching stops the reaction, reducing inaccuracy in titration results
what are some methods for quenching
- adding a suitable base/acid to neutralise reacting mixture
- sudden, rapid dilution w large quantity of water/any suitable solvent
- sudden, rapid cooling by plunging the mixture into ice
why is dilution an effective method for quenching?
- dilution lowers conc of reactants
- rate decr
how does cooling the mixture prevent further reaction from occuring?
- cooling lowers rate constant k
- thus rate decreases
the rate determining step is the [fast/slow] step
slow
do intermediates appear in the overall equation? [yes/no]
no
draw an energy profile diagram for a single step rxn
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draw an energy profile diagram for a multi-step (just 2 steps) rxn
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what are the requirements for an effective collision to take place?
- must collide
- in the correct orientation
- w sufficient energy to overcome activation energy of a reaction
what is activation energy? (short def.)
the minimum energy needed by the reactants for a reaction to occur
what are the factors that affect rate?
- surface area/conc/pressure (s/aq/g)
- temp
- catalyst
how does decr the size of the reacting solid affect rate
smaller particles -> larger SA -> incr frequency of effective collisions -> rate incr
how does incr concentration of reactant affect rate
incr conc -> more particles per unit vol -> incr frequency of effective collisions -> rate incr
how does incr the pressure of a system affect rate
incr pressure -> more gas particles per unit vol -> incr frequency of effective collisions -> rate incr
draw a boltzmann distribution curve to explain the effect of temperature on rate of reaction
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draw a boltzmann distribution curve to explain the effect of catalyst on rate of reaction
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what does a catalyst do?
it incr the rate of reaction by providing an alternative reaction pathway of lower Ea
draw a energy reaction pathway diagram for a catalysed reaction
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what are the two types of catalysts?
- homogenous
- heterogenous
what is are the two steps in the mode of action of heterogenous catalysts?
- adsorption
- desorption
what occurs in adsorption? (heterogenous catalysts)
- reactant molecules adsorb onto the active sites of the surface
- this lowers activation energy by:
- bringing reactant molecules closer together
- weakening bonds in reactant molecules
- it also correctly orientates the reactant molec
- products then desorb, freeing up active sites for new molecs
biological catalysts are also…
enzymes
