Rates of Reactions

RATES & REACTIONS




Rates ar measured either as a
'desay' of reactant or
'growth' of product




ㅿ ㄴ
All of these
graphs could show either :




concentration/volume/moles / mass us time



time time time
depending on what
you're measuring
decay of excess decay of
limiting growth of
product
reagent reagent
once the
graph has stabilized (whatever you measure no longer
OR (all used up ! ( ↑ limiting reagent used up

decay of reactant in
changes with time) ,
then the reaction has either completed / reached
a reversible reaction
equilibrium- you'll learn about this next section.




If we're
measuring concentration us time :




¤
_
gradient =
ㄻ
ㅰ
according to the definition :


O concentration
Rate of Reaction (ROR) & [reactants]
O concentration




{
rate of reaction
:

gradient 0 time
they'll bump
=
& time
-


more reactants means into eachother


rate of reaction and
gradient easily
: =
react more




time (s)


[reactants) 4 ROR4 gradient Rof ,
:
,: ,:. steep instantaneous gradients shown as tangents for inst .




[reactants] decreases used up RoRd gradient shallower
they get gets note how the the reaction
:
as : :
gradient shallows as
progresses
Creactants)
:
= 0 Lat least the
limiting). :
ROP =
0 :
gradient
=
0 (flat)

:
average RoR measured from the start of the graph to where it stabilizes




\




COLLISION
-




THEORY F
-

two events need to occur in order for reactants to become products :




must be oriented
reactants
correctly
-




X




must collide at the
right angle
√



When both of these criteria are fulfilled,


-

reactants must collide with enough SPEED (ana : Kinetic Energy / we
get an EFFECTIVE COLLISION




:
α
. . . . . . .
‰
&
X
even if oriented correctly ,
effective collisions & ROR

if have too little EK so if w find ways to ↑ number of effective
they , san




한. they will not react collisions ,
we can 4 ROR :




LEa )

:. EK > EA for reactants to react

, \




-
6 FACTORS AFFECTING ROR
i
Temperature
·

↑ temp =
↑ EK

… …
÷
' *
.... More molecules have EK >, EA faster =
mor erratic :
more
likely
∵ EK
↑
}
. "
…
per unit time bump
.... more collisions to into eachother
"
. ∴
.... more effective collisions unit time
:
不
per

.... ↑ ROR




2 Concentration

呆
. icons :
↑ consentration of a reactant more mole of reactant in same C =




per unit time amt of
space likely
: more
.... more collisions



.... more effective collisions per unit time to collide (this also ppressure
.... ↑ ROR




3 Volume measure of the number of collisions of gas with eachother and the sides the container
pressur is a
particles of


d volume = ↑ pressure

...
↑ conc of reactants




"
of particles smaller dre a
per unit time number in a


same
.... more collisions




:
-
avoume
.... more effective collisions per unit time


.... ↑ ROR




↑ Surface Area

↑ surface area =
↑ number of particles able to react

wr !!:::
·: "
more collisions
per unit time
....

ine
.... more effective collisions per unit time




欝
" -catalysts
.... more
particles hav EK>, EA
Catalysts are often inert metals (ot ,
Pd , Ni

.... more effective collisions per unit time
they help to correctly orientate particles (esp gases
.... ↑ ROR




6 Nature of Reactants


organic inorganic inorgania organic
-


vs


hydrochloric acid pentanoic acid

organic molecules tend to b larger
^


(^(
ㅐ



-o
... less likely to be correctly oriented …


H -

cl S
~ …

(
ー
c
- .
.

bonds to be broken which takes
they also have mor
longer ↓ * * i
have dRoRs compared
...
will usually to
inorganic particles

-



homogenous vs
heterogenous

homogenous
=
reactants all in same
phase & distributed equally

tosollide
more
likely effectively
:




-



homogenous > inorganic >
organic in terms of ROR




日