lecture 1 - chemical kinetics Flashcards

1
Q

what is kinetics the study of

A

study of rates of chemical reactions

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2
Q

what can kinetics give us insight into

A

insight into the mechanism of reactions

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3
Q

reactions have equations that correspond to them under certain conditions, why is this important

A

allows us to control how fast reactions take place

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4
Q

what industry is controlling reactions important in

A

chemical industry

slow: uneconomical
fast: dangerous

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5
Q

to study the rate we must

A

monitor the conc of at least 1 reactant

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6
Q

measuring conc inside the reaction vessel

A

in-situ measurement

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7
Q

measuring conc outside the reaction vessel

A

ex-situ measurement

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8
Q

how do ex-situ measurements occur

A

stop the whole reaction then measure conc

take sample from vessel and stop reaction in the sample

both stop reaction to measure conc

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9
Q

how can a reaction be stopped

A

quenching

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10
Q

what is quenching

A

stopping a chemical reaction
cool, dilute or neurtalise a reactant (all prevent the reaction from continuing)

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11
Q

what must we do after quenching

A

use analytical techniques to measure the conc of reactants or products

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12
Q

what must be done if a reaction is stopped to make an ex-situ measurement

A

we must repeat the experiment but stop the reaction at different times

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13
Q

in-situ measurement of conc examples

A

observation
spectroscopy
chemical sensor
gas pressure

measure conc without disturbing the reaction

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14
Q

how is spectroscopy insitu

A

u can gather info on the conc based on absorption of light!
this doesnt disturb the reaction

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15
Q

what do we need to measure rate

A

concentration as a function of time

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16
Q

over time, reactant conc

A

falls

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17
Q

over time, product conc

A

rises

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18
Q

rate of reaction at a specific time is given by

A

the gradient at that point

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19
Q

gradient equation

A

change y / change x

20
Q

gradient of a curve can be measured using a

21
Q

gradient can also be given by the differential of a math expression of a curve

A

gradient = d[A] / dt

22
Q

rate for reactants isss

A
  • gradient

rate must be a positive number

23
Q

rate for products isss

24
Q

what conc must be measured to find rate

A

conc of any product or reactant in the equation

25
if the reactants / products have stoichiometries (large numbers in front of them) we must
divide gradient by the stoichiometry multiply the gradient by 1/stoichiometry
26
finding the initial rate of reaction
gradient where t=0
27
what is a rate law
equation of a reaction based on a conc as a function of time rate = k [a][b]
28
how can we see what order a reactant is
the power
29
overall order for a reaction is
powers added together
30
what is k
rate constant
31
what does k depend on
temperature k for kelvin ;)
32
what does k not depend on
concentrations
33
how can we determine rate law
keep temp constant or it will affect k!!! sometimes based on how many molecules are reacting (its molecularity) in single step reactions!!
34
what is the rate determinding step
slow step of the reaction makes up the rate law
35
0th order rate law equation
rate = k reaction occurs at a constant rate until all reactants are consumed, then stops
36
but how can we determine rate laws if its not based on molecularity
we must carry out experiments
37
what is the integrated rate laws
single reactant shape of curve tells u the order plot date in diff ways to find the order EXCELLLLL
38
initial rates method
slow reactions measure the initial rate of a reaction at different starting concentrations
39
isolation method
determines order when there are multiple reactants
40
units for rate constant
moldm-3 s-2 / moldm-3 (conc)
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