6+16: kinetics

Question 1

for 0 order, the rate of the reaction is _____________ of [rxt]

Answer 1

independent

Question 2

which order of reaction is the rate directly proportional to [rxt]?

Answer 2

1st order

Question 3

for 2nd order, rate is directly proportional to…

Answer 3

[A]2

Question 4

draw the conc - time graph for 0 order

Answer 4

-

Question 5

draw the conc - time graph for 1st order

Answer 5

-

Question 6

draw the rate - conc graph for 2nd order

Answer 6

-

Question 7

draw the rate - conc graph for 0 order

Answer 7

-

Question 8

draw the rate - conc graph for 1st order

Answer 8

-

Question 9

draw the conc - time graph for 2nd order

Answer 9

-

Question 10

what is the equation for half-life

Answer 10

t1/2 = ln2/k

Question 11

t1/2=lnk can only be used for _______ order reactions

Answer 11

1st

Question 12

what is the equation used to find the number of half lives for 1st order reactions?

Answer 12

Ct/Co = (1/2)^n

Ct – [ ] at time t
Co – initial [ ]
n – no. of half lives

Question 13

what methods can be used to measure the volume of gas produced?

Answer 13

• gas syringe
• water displacement method

Question 14

how can changes in mass be measured?

Answer 14

with an electronic balance

Question 15

if a reactant is iodine, what chemical method of analysis can be used?

Answer 15

clock reaction

Question 16

what does quenching mean?

Answer 16

it means stopping the rxn

Question 17

why must quenching be done in titration?

Answer 17

quenching stops the reaction, reducing inaccuracy in titration results

Question 18

what are some methods for quenching

Answer 18

• 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

Question 19

why is dilution an effective method for quenching?

Answer 19

• dilution lowers conc of reactants
• rate decr

Question 20

how does cooling the mixture prevent further reaction from occuring?

Answer 20

• cooling lowers rate constant k
• thus rate decreases

Question 21

the rate determining step is the [fast/slow] step

Answer 21

slow

Question 22

do intermediates appear in the overall equation? [yes/no]

Answer 22

no

Question 23

draw an energy profile diagram for a single step rxn

Answer 23

-

Question 24

draw an energy profile diagram for a multi-step (just 2 steps) rxn

Answer 24

-

Question 25

what are the requirements for an effective collision to take place?

Answer 25

1. must collide 2. in the correct orientation 3. w sufficient energy to overcome activation energy of a reaction

Question 26

what is activation energy? (short def.)

Answer 26

the minimum energy needed by the reactants for a reaction to occur

Question 27

what are the factors that affect rate?

Answer 27

1. surface area/conc/pressure (s/aq/g) 2. temp 3. catalyst

Question 28

how does decr the size of the reacting solid affect rate

Answer 28

smaller particles -> larger SA -> incr frequency of effective collisions -> rate incr

Question 29

how does incr concentration of reactant affect rate

Answer 29

incr conc -> more particles per unit vol -> incr frequency of effective collisions -> rate incr

Question 30

how does incr the pressure of a system affect rate

Answer 30

incr pressure -> more gas particles per unit vol -> incr frequency of effective collisions -> rate incr

Question 31

draw a boltzmann distribution curve to explain the effect of temperature on rate of reaction

Answer 31

-

Question 32

draw a boltzmann distribution curve to explain the effect of catalyst on rate of reaction

Answer 32

-

Question 33

what does a catalyst do?

Answer 33

it incr the rate of reaction by providing an alternative reaction pathway of lower Ea

Question 34

draw a energy reaction pathway diagram for a catalysed reaction

Answer 34

-

Question 35

what are the two types of catalysts?

Answer 35

- homogenous - heterogenous

Question 36

what is are the two steps in the mode of action of heterogenous catalysts?

Answer 36

1. adsorption 2. desorption

Question 37

what occurs in adsorption? (heterogenous catalysts)

Answer 37

- 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

Question 38

biological catalysts are also...

Answer 38

enzymes