Lecture notes
Module 5 ocr chemistry notes
- Module
- Physical Chemistry (H432)
- Institution
- OCR
Covers all the content in module 5 chemistry in detail
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OCR Tr 2 PhysicalChemistry Notes
, How fast ? gas constant = 8 .
314
How an rate de measured experiment
·
Change implt - Alt overtime
pltmeter
·
regular interval . l It' incunc
*
Mass Lost
that balarec
reach on
produce gas! Place on
·
reachin
volume of : Gas syringe
gas produced speaked perod of time ide gas equation
·
over . Use
"Colow change" Colorimeter : Measures ansurbance of light -
more conce darker more light absorbed
.
12ca9s + Cl3 COCIsca9s -
City COCH2 lag) + Tags + H cags
Noprud lefts
Brown Colorless - All products colorless
.
-
Known diff of 12
plut calibration absorbance plot graph
·
cove .
conc measure on -
Calculating rate from graph
a
By
↳ rate (how fast) -
gradict c
·
Tangent
Tangent
·
Initial rate from graph -
·
use target & O minutes
Clock epenments
· how long it takes until we can't see cross
through beaker. colow change -
end point
↑
quicker clock . Lester Ital rate of reacher .
·
Bassumphuns
·
tenn of reache remaus constant
of
Concentrate reacher does not
change significantly during the time paned of the
·
.
reacher
·
rachon has not proceeded too so when the end punt is see
-
rate of reachin remains constand doing time period measuries
Lodine Clock experiment
-
H2Ozcaas + 2Httca9s + 21-aags - 2 H2Ock + laccas
·
2S20s" + lecass- 2 lcaas + S40 .
"cass-when sodium tho sulfat reacts comi I reacts
with stack
gives deep blue /black color .
Change conce
~
, keep every thing else constances find order of rechon.
Rate Equahon Orders
Link Oste vol conc can of substance A+ B -*
C + 1)
~
rate = K [A]" [B] "orders of reaches : tall i how care of substance affects the rate -
·
moldm"s"'varccurent
·
Zero order : Aconc has no effect on rate e .
g
18 [A] x 2 rate doesn't
·
1st order ! Aconc has proportional change on rate .
e
.
g
18 [A]42 , ratcxz
2 18 [A] doubles than quadruples
↳ order : squared proportuna change on rate . rare
can only he determined experimetely
, Rare Eg Rate constant
· ↳ : allows as to equate rate concentration. only fisced o particular temp . A temp , Dk
Larger faster rate of reachun
. ↑ temps * Kinche , collide morc often , but conc remains constant
to make equance balanced value of K
=
Calculating rate
↑ Locample :
2NOcgs Orcgs
·
+ -
2N02cgs-reachen 2 order not resport to NO & 1st order col respect to 02
Calculate rate of reache
given conc
of NO" 3x10-3 On (10-3 . E = 700
, 000 Moldest
b
[B]
"
rate
: k [A]
= (100 , 000 mol-dm's' [3x10-3]" [110-3J't
-6 :
3 X10- Moldest
Calculating Rate Constant
Example : Nocg + COcgs + Dacgs-NOzg + (Ocg) ·
K :? NO second order , [0s02 zerwarder
curd = 1 .
5410"moldm rate of reache : 1 11 x10- moldm-3 su
.
rate : " [NO]
↳ : = (1 . 173 x 10" "moldmst) =
520 mol"dms"
o (1 .
5410-3 Moldo's 72
Rate Graphs
~ rare found by taking gradient a various points on a concentration-time .
graph
↳ rate concentrative graphs help us
identify the order
changes
in
rate constant rate anonles
· I equal
-
1 order
O
E o
② order Change in canc Changes
·
T
rare equally
Time
(As time A
Vieuanelamots
ratechanges -
2nd order
?
↳
e
Time [A]
Half-life
· time it takes for half of the reactants to be used un- graph used to calcaltck
↳ 195 order reachers : half life independent of concentrates . Half life same length
.
t
Kee
Unt :
Initial Rates method
* repeat experiments several times but changing con cf A B > Jone & ahme ble
, wano know effects of
Changing
canc of each one on rate
Work out initial
· rate of each experiment
record concentratues of each experiments ther initial rates instable -
Workout orders wite rate equation
· Example
r = k [NOcgc] 2 Clecgn]
Tate 1 0 .
63 C122 1 order
NO = List order 0 63 : k
.
[NUcgs] + [Cl2cqc]
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