Download Ce ( IV)

CERIMETRI
SMK Negeri 13 Bandung
PRINCIPAL
Based on reduction Ce4+ becomes Ce3+
by reducing agent
Reaction of reduction Ce4+:
Ce4+ + e  Ce3+
2
The Characteristics and Advantages
Ce (IV
 In solution there is only in condition
of Ce4+ and Ce3+
 A real strong oxidant matter in a
stong
acid
situation,
potential
reduction in H2SO4 1-8 N as big as
1.43 ± 0.05 Volts. If the solution is
neutralized, power oxidant declines
because of hydrolysis.
 Ce (IV) solution very stable for long
time in H2SO4 solution. Doesn't
require protection from light, and can
be boiled with a flash in the pan
3
without changing concentration
The Characteristics and Advantages Ce (IV
 Can be used in determination of reducer
matters in high concentration of HCl.
 Ce (IV) 0,1N Solution is not too colourfull
so, it is easy to read miniscus
 In reaction of Ce ( IV) salt at acid solution
with
reducer
matters,
change
of
its
oxidation number is :
Ce4+ + e ⇄ Ce3+, hence BE = Mr
4
The Characteristics and Advantages Ce (IV)
 Ce(SO4)2 is multipurpose oxidant, can be used
widely. Most all matters which can be titrated by
KMnO4 also can be standardized with Ce(IV)
 Ce ( IV) can be used for determination of iron in HCl
solution without reactant Zimmermann-reinhardt
 Ce(SO4)2 Solution is best standardized with arsen
oxide. Other matter of which can be applied that is;
sodium oksalat, pure iron, potassium ferosianida
anhidrous and amonium ferro sulphate.
5
The Characteristics and Advantages Ce
(IV
Cerium in chloride acid is very unstable,
reaction:
2Ce4+ + 2Cl ⇄ 2Ce3+ + Cl2
so that HCl cannot be
oxidation with excessive
cerium.
used in
sulphate
But direct titration with sulphate
cerium in dilute medium HCl at room
temperature, can be done.
6
Potential of Ce(iv) in Acid 1M
 HClO4
: + 1.70 V
 HNO3
: + 1.61 V
 H2SO4
: + 1.44 V
 HCl
: + 1.28 V
7
Preparation of Ce(SO4)2 standard solution
1. From cerium amonium ( IV) nitrate
2. From cerium ( IV) sulphate
3. From cerium amonium ( IV)
sulphate
4. From cerium ( IV) hydroxide
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Preparation of Ce(SO4)2
standard solution from cerium amonium ( IV) nitrate
 28 g ( NH4)2Ce(NO3)6 pa is dissolved with 100 ml aquadest
in chemical glass 600 l
 Adds dilute NH4OH (± 60 ml NH4OH 2,5N) slowly, keep
stirring until NH4OH excessive
 Filters Ce(OH)4 formed with Sintered-glass
 Wash precipitate 50 ml aquadest for 5 times, and lets
precipitate during 30 minutes on sintered- glass
9
Preparation of Ce(SO4)2 standard solution
from cerium ammonium ( IV) nitrate
- Removes precipitate into beaker glass, rinses
precipitate remaining with 4x50 ml sulphate acid 2M
which has been heated beforehand at temperature
600C
- Heats precipitate until precipitate dissolve perfectly
- Cooling the solution, carries over into volumetric
flask 500 ml, makes it to the mark with aquadest,
standardization beforehand before applied
10
Preparation of Ce(SO4)2 standard solution from
cerium ammonium ( IV) nitrate
Way of 2
- 55,0 g ( NH4)2Ce(NO3)6 pa is evaporated in
evaporation
dish
until
dry
approximant
with
excessive H2SO4 concentrate( 48 ml) .
- Dissolves residue yielded in H2SO4 1M.
- Removes in volumetric flask 1L, adds sulphate acid
1M until near by border, mark it up with addition
aquadest,
standardization
beforehand
before
applied. .
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Preparation of Ce(SO4)2 standard solution from cerium
ammonium ( IV) nitrate
Ce(SO4)2
- Weight out 35-36 g pure Ce(SO4)2 into chemical
glass 600 ml.
- Adds 56 ml H2SO4 1:1, swirled with slow warm-up
until incessant salt.
- Carries over into volumetric flask 1L is corking glass.
- Dilute with aquadest until to the mark.
-
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Preparation of Ce(SO4)2 standard solution from
cerium ammonium ( IV) nitrate
(NH4)4[Ce(SO4)2].2H2O
- Weight out 64-66 g (NH4)4[Ce(SO4)4]2H2O pure, put
into 28 ml H2SO4 solution /500 ml aquadest.
- Swirled solid matter until dissolve then carries over
into volumetric flask 1L, dilute it into the mark.
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Preparation of Ce(SO4)2 standard solution from cerium
ammonium ( IV) nitrate
Ce(OH)4
- Placed 21 g Ce(OH)4 in chemical glass 1.5 l
- Adds be swirled by 100 ml H2SO4.
- Stirs and adds 300 ml aquadest slowly and carefully.
- Hushed one night, if there are residue, filtered it.
Filtrate carried over into volumetric flask 1L, dilute until
to the mark.
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Preparation of Ce(SO4)2 standard solution from
cerium ammonium ( IV) nitrate
 Recrystallization
 Eliminates ions
 Forms of sulphate cerium
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Recrystallization
125 grams (NH4)2Ce(NO3)6 technical
dissolved in 100 ml HNO3 1:3 and 40
grams NH4NO3
Heats then filters in a state of
temperature with sintered- glass.
Made cool the filtrate in ice, filters
crystal formed with sintered - glass
and continues suction during 1-2
hours that rest of nitrate acid
castaway.
oC.
Dries crystal at temperature 80-85 16
Eliminates ions
Weight out 28 grams dry crystal,
dissolve in 100 ml water.
Add 60 ml NH4OH 2,5 N little by little
while stirring until precipitate is
formed.
Filter precipitate with sintered - glass
and cleans with 5 x 50 ml water in
order to NH4NO3 castaway.
Continues suction during 30 minutes
in order to the rest of water
castaway.
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To form of sulphate cerium
Removes precipitate into chemical
glass and rinses sintered - glass with
50 ml Warm H2SO4
4 N ( 60 oC).
Stir while heating in order to make
precipitate dissolved, makes cool.
Carries over in volumetric flask 500
ml then mark it up.
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Standardization Standard Solution Ce ( IV)
1. With As2O3
2. With pure iron
3. With Na2C2O4
4. With salt Mohr
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Standardization Standard Solution Ce ( IV) with
As2O3
-
-
-
Weight out 0.2 g As2O3 pa, carries
over in chemical glass 400 ml or
erlenmeyer 350 ml.
Adds 20 ml NaOH 2M, heats slow
until dissolving perfectily, makes
cool finite of room temperature.
Adds 100 ml aquadest + 25 ml H2SO4
2.5 M + 3 drip osmium tetroksida
0.01 M and 0.5 ml indicator
fenilantranilat or 12 drips ferroin.
Titration with Ce(SO4)2 0.1 N until
colour
changed
(
red-orange
becomes pale blue)
Do triplo.
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Standardization Solution. Standard Ce ( IV) with As2o3
Reactions:
As2O3 + 4OH- → 2HAsO32- + H2O
2Ce4+ + HAsO32- + H2O → 2Ce3+ +
HAsO42- + 2 H+
At equivalence point, mek Ce4+ = mek
HAsO32The most precise indicator is ferroin
with Eo = 1.06 Volts or fenilantranilat
with Eo = 0.89 Volts
Required existence of osmium
tertroxide catalyst because the
reaction is very slow at room
temperature.
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Standardization Standard Solution Ce ( IV)
with Pure Fe
-
Weight out accurately 0.2 grams of pure
iron strand of metal
-
Put into chemical glass 150 ml
-
Add 20 ml HCl 1:1 then heat on the steam
bath until all irons dissolves
-
Add Sncl2 drip for the shake of drip until
solution do not having colour or becoming
green very young then adds 1-2 drips
excessive SnCl2
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Standardization Standard Solution Ce ( IV) with
Pure Fe
-
Made cool under current, then poured 20
mL saturated solution HgCl2 at the same
time, lets during 3 minute
-
Rinses the solution into erlenmeyer flask
500 mL + 2 drip feroin indicator
-
Titration with Ce(SO4)2 until the colour
changed from pink become pale yellows.
-
Do blanko standarization
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Standardization Standard Solution Ce ( IV) with
Pure Fe
Reactionsi:
2Fe + 6HCl → 2FeCl3 + 3H2
2Fe3+ + Sn2+ → 2Fe2+ + Sn4+
Fe 2+ + Ce4+ → Fe3+ + Ce3+
 At equivalence point, mek Ce4+ = mek Fe2+ =
mek Fe
 The most precise indicator is ferroin with Eo
= 1.06 Volt or fenilantranilat with Eo = 0.89
Volt
 Sncl2 applied must be fresh, because SnCl2
can be oxidized by air
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 HgCl2 added to oxidize rest of SnCl2
Standardization Standard Solution Ce ( IV) with Na2C2O4
-
-
-
Weight out accurately 0.2 grams
Na2C2O4 pa. then puts it into erlenmeyer
flask 250 ml.
Adds 25-30 mL H2SO4 1 M then heats
finite of temperature 60 oC then adds 30
mL Ce(IV) which will be standardized,
drip for the shake of drip
Re-heats finite 60 0C then added 10 mL
Ce(IV) which will be standard, re-heats
finite 600C then added 10 mL Ce(IV)
which will be standardized and hushed
during three minutes.
Made cool and back-titration of excess
Ce(IV) with iron ( II) solution with
indicator ferroin.
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Standardization Standard Solution Ce ( IV) with Na2C2O4
 Reactions:
C2O42- + 2Ce4+ → 2CO2 + 2Ce3+
Ce4+ + Fe2+ → Ce3+ + Fe3+
 The most precise indicator is ferroin with
Eo = 1.06 Volts or fenilantranilat with Eo =
0.89 Volts
 Done heat-up because reaction between
Na2C2O4 takes place quickly at high
temperature.
 Applied back-titration procedure because
redox indicator will be oxidized at high
temperature.
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Standardization Standard Solution Ce ( IV)
with Mohr salt
Way of 1
- Weight out accurately 1 gram Mohr
salt, dissolves with H2SO4 4 N and
rinse into volumetric flask 250 ml
with water of O2 free
- Pipette
25
ml
solution
into
Erlenmeyer flask, adds to depth 25
mL H2SO4 1 N and 6-8 drips ferroin
- Titration with Ce(IV) solution until
colour changed from red to green
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Standardization Standard Solution Ce ( IV)
with Mohr salt
Way of 2
- Pipette 25 mL Ce ( IV) solution then
acidified and adds ferroin
- Titration with standard solution of
finite Mohr salt until colour changed
from green becomes red
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Standardization Standard Solution Ce ( IV) with
Mohr salt
Reactions:
Fe
2+
+ Ce4+ → Fe3+ + Ce3+
At equivalence point, mek Ce4+ = mek
Fe2+
The most precise indicator is ferroin
with Eo = 1.06 Volts or fenilantranilat
with Eo = 0.89 Volts
Mohr Salt dissolved in free water of
O2 to prevent oxidation of Mohr salt
by O2 in water.
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What is going on at the time of
end point?
Indicator turns colour because
indicator experiences oxidation ( if
Ce4+ in burette) or reduction ( if done
titration indirectly / back-titration).
oxidation of Indicator happened if
Fe2+ has used up/finished reacts and
potential solution has reached
potential reduction indicator value
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Determination of (NO2-)
Weight out accurately 2 ml sample
solution of nitrite then dilutes in
volumetric flask 250 ml with free
water of O2.
Removes 50 ml standard solution Ce (
IV) into Erlenmeyer flask, acidifies
with H2SO4 4 N.
Pipette 25 mL of nitrite solution
sample and adds into Ce ( IV)
solution in Erlenmeyer flask carefully
with pipette tip as near by possible
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with surface of Ce ( IV) solution.
Determination of (NO2-)
Lets during 5 minutes.
Adds 6-8 indicator drips ferroin.
Titration with standard solution ferro
until colour changed from green to
become red.
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Determination of (NO2-)
NO2- + 2Ce4+
2H+
Reactions
+ H2O → NO3- + 2Ce3+ +
excess
Ce4+ + Fe2+ → Ce3+ + Fe3+
excess
mek Fe2+
= mek Ce4+ excess
mek Ce4+ excess
= mek Ce4+ - mek
NO2mek Fe2+
= mek Ce4+ - mek NO2mek NO2= mek Ce4+ - mek Fe2+
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Determination of (NO2-)
 Nitrite easy to be oxidized by O2, therefore
water applied as nitrite sample solvent must
free of O2 and position of when adding
nitrite sample must as near by possibly, to
obviate contact with air.
 It is not done direct titration because nitrite
easy to be oxidized by air and can react with
air during shaking process.
 The most precise indicator is ferroin with Eo
= 1.06 Volts or fenilantranilat with Eo = 0.89
Volts
 Colour changed when end point, green
become red
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