lecture 1 - chemical kinetics

Question 1

what is kinetics the study of

Answer 1

study of rates of chemical reactions

Question 2

what can kinetics give us insight into

Answer 2

insight into the mechanism of reactions

Question 3

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

Answer 3

allows us to control how fast reactions take place

Question 4

what industry is controlling reactions important in

Answer 4

chemical industry

slow: uneconomical
fast: dangerous

Question 5

to study the rate we must

Answer 5

monitor the conc of at least 1 reactant

Question 6

measuring conc inside the reaction vessel

Answer 6

in-situ measurement

Question 7

measuring conc outside the reaction vessel

Answer 7

ex-situ measurement

Question 8

how do ex-situ measurements occur

Answer 8

stop the whole reaction then measure conc

take sample from vessel and stop reaction in the sample

both stop reaction to measure conc

Question 9

how can a reaction be stopped

Answer 9

quenching

Question 10

what is quenching

Answer 10

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

Question 11

what must we do after quenching

Answer 11

use analytical techniques to measure the conc of reactants or products

Question 12

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

Answer 12

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

Question 13

in-situ measurement of conc examples

Answer 13

observation
spectroscopy
chemical sensor
gas pressure

measure conc without disturbing the reaction

Question 14

how is spectroscopy insitu

Answer 14

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

Question 15

what do we need to measure rate

Answer 15

concentration as a function of time

Question 16

over time, reactant conc

Answer 16

falls

Question 17

over time, product conc

Answer 17

rises

Question 18

rate of reaction at a specific time is given by

Answer 18

the gradient at that point

Question 19

gradient equation

Answer 19

change y / change x

Question 20

gradient of a curve can be measured using a

Answer 20

tangent

Question 21

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

Answer 21

gradient = d[A] / dt

Question 22

rate for reactants isss

Answer 22

• gradient

rate must be a positive number

Question 23

rate for products isss

Answer 23

gradient

Question 24

what conc must be measured to find rate

Answer 24

conc of any product or reactant in the equation

Question 25

if the reactants / products have stoichiometries (large numbers in front of them) we must

Answer 25

divide gradient by the stoichiometry

multiply the gradient by 1/stoichiometry

Question 26

finding the initial rate of reaction

Answer 26

gradient where t=0

Question 27

what is a rate law

Answer 27

equation of a reaction based on a conc as a function of time

rate = k [a][b]

Question 28

how can we see what order a reactant is

Answer 28

the power

Question 29

overall order for a reaction is

Answer 29

powers added together

Question 30

what is k

Answer 30

rate constant

Question 31

what does k depend on

Answer 31

temperature

k for kelvin ;)

Question 32

what does k not depend on

Answer 32

concentrations

Question 33

how can we determine rate law

Answer 33

keep temp constant or it will affect k!!!

sometimes based on how many molecules are reacting (its molecularity) in single step reactions!!

Question 34

what is the rate determinding step

Answer 34

slow step of the reaction
makes up the rate law

Question 35

0th order rate law equation

Answer 35

rate = k
reaction occurs at a constant rate until all reactants are consumed, then stops

Question 36

but how can we determine rate laws if its not based on molecularity

Answer 36

we must carry out experiments

Question 37

what is the integrated rate laws

Answer 37

single reactant
shape of curve tells u the order

plot date in diff ways to find the order

EXCELLLLL

Question 38

initial rates method

Answer 38

slow reactions
measure the initial rate of a reaction at different starting concentrations

Question 39

isolation method

Answer 39

determines order when there are multiple reactants

Question 40

units for rate constant

Answer 40

moldm-3 s-2
/ moldm-3 (conc)