book kinetics

Question 1

rate of reaction definition

Answer 1

rate at which reactants are converted into products

Question 2

what is easured when measuring rate of a reaction

Answer 2

measure formation of products

consumption of reactants

Question 3

what is a kinetics profile

Answer 3

graph of conc against time that shows how fast conc changes as the reaction proceeds

Question 4

what do we plot when looking at rate of reaction

Answer 4

concentration against time

Question 5

rate of reaction at a particular time

Answer 5

find the gradient (y/x)

rate must be positive

Question 6

initial rate is the

Answer 6

rate at 0 time

tangent on 0 + gradient at 0

Question 7

units for rate of reaction if conc is in moldm-3

Answer 7

mol dm-3 s-1

Question 8

units for rate of reaction of a gas whrn units are Pa

Answer 8

Pa s-1

Question 9

gradient of line or rate at particular time in terms of differentials

Answer 9

d[a] / dt

Question 10

what affects the rate of reaction

Answer 10

conc
temp
catalyst

surface area of solid
radiation intensity
solvent nature

Question 11

what is rate constant k

Answer 11

constant that relates the speed of the reaction to a certain condition, normally temp.

Question 12

does rate law / rate equations use reactant conc or product conc

Answer 12

reactant conc

Question 13

rate law / rate equation example

Answer 13

k [rea] [rea]

Question 14

why do we need integrated rate equations

Answer 14

rates of reaction cannot be measured directly.

exp data usually consists of pro and rea conc measurements at different times.

integrated rate laws give an expression that shows how conc varies with time.

Question 15

IRL of conc of rea A at time t

Answer 15

[A]t

Question 16

IRL of conc of rea A at the start of the rea

Answer 16

[A]0

Question 17

IR for first order reaction:
A -> B

Answer 17

ln [A]t = ln[A]0 - kt

if k and ln[A]0 are known, conc of A at any time can be found

Question 18

what do u plot on the graph for 1st order rea

Answer 18

ln[A] against time

gradient = -k

Question 19

IRL straight line edition for 1st order

Answer 19

ln[A]t = -kt + ln[A]0

y = mx + c

Question 20

IRL for second order rea

Answer 20

1/ln[A]t = 1/ln[A]0 + 2kt

Question 21

IRL straight order version for 2nd order

Answer 21

1/ln[A]t = 2kt + 1/ln[A]0

Question 22

what do we plot for a 2nd order rea

Answer 22

1/[A] against time

2k = gradient

Question 23

half life definition

Answer 23

t 1/2

time taken for conc of reactant to fall to half its initial value

Question 24

half life equation first order

Answer 24

t1/2 = ln(2) / k

Question 25

half life equation 2nd order

Answer 25

t1/2 = 1 / 2k [A]0

Question 26

how must a rate equation be determined

Answer 26

experiments
to see how rate depends on conc of each reactant. in order to find the order.

Question 27

if the conc change of a reactant has no effect on the rate it isss

Answer 27

0th order
doesnt appear in the overall rate equation

Question 28

what is the reactions mechanism

Answer 28

series of elementary steps that make up the whole reaction (complex reactions, reactions with more than one step)

Question 29

isolation method

Answer 29

put one reactant in excess so its initial conc is the same as its conc throughout the reaction.

find the effect of 1 rea conc on rate,

then switch and repeat for the other reactant.
these will give us pseudo rate constants.

Question 30

initial rates method

Answer 30

gradient is found for t=0 - ror at start of reaction
initial rate

repeat for different starting concentrations

conc is plotted against time

conc ust be monitored throught and plotted in order to get a graph to find t=0

Question 31

each elementary step has its own

Answer 31

rate constant

Question 32

the rate determining step is the

Answer 32

slowest step
slowest mechanism

Question 33

what is a concerted reaction

Answer 33

when rea turns into pro in a single step

Question 34

if a rate constant has a larger value that means the reaction is

Answer 34

faster

Question 35

k is …. for a given temp

Answer 35

constant

Question 36

rate is …. for a given temp

Answer 36

not constant
usually changes during the reaction.

Question 37

what does the term e -Ea/RT mean

Answer 37

fraction of collisions that have the required energy

Question 38

what happens to e -Ea/RT as temp increases

Answer 38

the value gets smaller, it gets closer to 0

e0 = 1

1 means all collisions have enough energy.
so k = A

Question 39

what is A in arrhenius

Answer 39

pre exponential factor
same units as k

rate constant value if all the collisions have enough energy to overcome the energy barrier aka the activation energy.

Question 40

what is the arrhenius equation

Answer 40

k = Ae -Ea/RT

equation that describes how the rate constant varies with temperature

Question 41

what is Ea

Answer 41

activation energy
Jmol-1
energy barrier reactants need to overcome in order to form products

Question 42

how does rate constant increase with temp

Answer 42

a greater fraction of the reactant molecules have enough energy to pass over the energy barrier.

more reaction molecules have or have above the Ea value.

Question 43

what happens in the collision theory

Answer 43

used to find approx value of A.

for a reaction to occur, 2 molecules must collide with a certain minimum kinetic energy.

the Ke must be equal to or larger than the Ea.

Question 44

what is kinetics

Answer 44

study of the rates of chemical reactions