Iodometric
Iodometric
The
titrimetric iodometric analysis indirectly to substances that are
oxidizing agents such as iron III / Fe (III), copper II / Cu (II). Iodometric
titration can be used untukmenetapkan compounds having a lebihbesar
oxidation potential than the iodine-iodide system or compounds that are
oxidizing agents such as CuSO4.% H2O.
On
iodometric method, the sample will be reduced by oxidizing KI
(potassium iodide) is excessive and will result in I2 (Iodine) which
would then be in ttrasi by Na2S2O3 (sodium thiosulfate). Banyakknya
volume of Na2S2O3 (sodium thiosulfate) was used as titrant equivalent to I2 (iodine) and produced equivalent levels of the sample.
Standard solution used in the iodometric method is Na2S2O3 (sodium thiosulfate). Salt
is usually shaped in the form of pentahydrate or Na2S2O3.5H2OLarutan
not be distandaarisasi by weighing directly, but must be standardized
with the standard primer.Karena Na2S2O3.5H2O unstable in the long-term
storage.
On
iodometric method of examination should be kept stable pH (hydrogen
pondus). Solution should be maintained at a pH of less than 8.Karena if
the pH is more than 8 or in an alkaline I2akan react with hydroxide
(OH-) to form the next hyphoiodit Iodides and iodide, and decomposes
into Iodidat which can oxidize thiosulfate to run the reaction sulfat.Sehingga not quantitative.
This
method uses an indicator on Amylum 1%. Amylum have properties difficult
to dissolve in water and unstable in water suspension to form complex
compounds poorly soluble in water when reacting with iodium.Sehingga
penanbahan Amylum as indicators should not be added at the beginning
reaksi.penambahan Amylum as an indicator should be given towards the end point titration (at the time of pale yellow solution).
Titration
end point is marked with blue color changes into a clear solution (from
blue to blue hilang.Jadi addition of starch is carried out as it
approaches the titration end point is so that starch does not wrap as it
will cause the starch iodine titrated difficult to return to the
original compound. Process of titration should
be done as soon as possible, this is due to the easy nature of I2
menuap. At the titration end point that is bound iodine also reacts with
the titrant lost so suddenly disappeared and the blue color changes are
very obvious. Use of this indicator is to clarify the solution color
changes that occur at the end point titration.
sensitivity of the color depends on the solvent used. iodine-starch
complex has a small solubility in water, so it is generally added at the
titration end point. If a solution of iodine in KI in the neutral
atmosphere is titrated with sodium thiosulfate, then:
-+ I3-3I-+ 2S2O32 S4O62-
S2O32-+ I3-2I-+-S2O3I
2S2O3I-+ I-+ I3-S4O62-
S2O3I-+-S4O62 S2O32-+ I-
Sodium
thiosulfate (Na2S2O3.5H2O) can be easily obtained in a high state of
purity, but there's always a little uncertain of the exact water
content, has particularly karenaNa2S2O3.5H2O flouresen or decaying
properties of the salt-cracked and unstable in the long-term storage. Therefore, these substances are not eligible to serve as the primary standard stock solutions. Sodium thiosulfate (Na2S2O3.5H2O) is a reducing agent, with the following equation:
2S2O32-S4O62-+ 2e-
Standardization
of sodium thiosulfate (Na2S2O3.5H2O) can be done using potassium
iodate, potassium chromate, copper and iodine as the primary standard
solution, or with potassium permanganate or cerium (IV) sulfate as the
secondary standard solution. But
in this experiment the compound used in the process of standardization
of sodium thiosulfate (Na2S2O3.5H2O) is potassium iodate (KIO3)
standards.
Solution
of sodium thiosulfate (Na2S2O3.5H2O) before being used as a standard
solution in the iodometric process should be standardized in advance by
potassium iodate (KIO3) which is the primary standard. Solution of potassium iodate (KIO3) iniharus added with concentrated sulfuric acid, the color of the solution became clear. And after adding the potassium iodide (I2), the solution becomes dark brown. Function
of the addition of concentrated sulfuric acid (H2SO4 PA) in the
solution is to give the acid, because the solution consisting of
potassium iodate (KIO3) and klium iodide (KI) is in neutral or has a low
acidity.
His reaction is as follows:
IO3-+ 5I-+ 6H + → 3I2 + 3H2O
Determination of levels of Cu2 + by Standard Na2S2O3 solution
In
the determination of Cu by standard Na2S2O3 solution will be some
change in color of the solution before the titration end point. Pure
copper can be used as a primary standard for thiosulfate and sodium
thiosulfate should be recommended if it is used to determine copper. Standard pair potential Cu (II) - Cu (I) is +0.15 V and therefore iodine is a better oxidizing agent than the ion Cu (II). But when the iodide ion is added to a solution of Cu (II) will precipitate formed Cu (I).
2Cu2 + + 4I-2CuI (s) + I2
Determination
of Cu2 + in solution with the help of a solution of sodium thiosulfate
performed diluting 5 mL sample of the salt to 100 mL and taking 10 mL of
dilution is to be added to a solution of KI 10%, and titrate with
standard solution of sodium thiosulfate until the solution of the
original dark brown to a solution of a pale yellow. Then
the solution was added with 2 mL of 1% starch solution initially
produces pale yellow to dark blue, addition of 1% starch indicator is
intended to clarify the color changes that occur in the solution. then the solution is back titrated with sodium thiosulfate solution until the blue color of the solution right away. To
further clarify the occurrence of the reaction, is added to a solution
of I2 with starch amilum.Bertemunya this will cause any blue-colored
solution kehitaman.Selanjutnya titration is continued until the blue
color disappears and a cloudy white.
I2 + I2-starch starch
2S2O32 + I2-starch-2I-+ S4O6 + starch-
Things
to consider after the addition of starch is the nature of the
adsorption on the surface of the deposition of copper (I) iodide. These
properties lead to the absorption of iodine and where iodine was
removed by titration, the titration end point will be reached too
quickly. Therefore,
prior to the titration end point is reached, when the color of the
solution is titrated with Na2S2O3akan changed from blue to clear, the
addition of potassium thiocyanate KCNS.
REFERENCES
Basset.J etc. Festive 1994.Buku Vogel, Quantitative Analysis of Inorganic Chemistry. Book Medical Publishers EGC. Jakarta.
Day RA. Jr. and Al Underwood.1992. Quantitative Chemical Analysis. Sixth Edition.: Erlangga.Jakarta
Khopkar, S. M. 1990. Basic Concepts of Analytical Chemistry. University of Indonesia Press. Jakarta.
Rivai, Harrizul. Of 1995. Chemical Examination of principle. Publisher UI. Jakarta.
iodometri
Iodometric
Iodometric
Die titrimetric iodometric analise indirek stowwe wat oksideermiddels soos yster III / Fe (III), koper II / Cu (II). Iodometric
titrasie gebruik kan word untukmenetapkan verbindings met 'n lebihbesar
oksidasie potensiaal as die jodium-jodied of verbindings wat
oksideermiddels soos CuSO4% H2O.
Op
iodometric metode, die monster verminder word deur oksiderende KI
(kaliumjodied) is oormatige en sal in I2 (Jodium) wat sou dan wees in
ttrasi Na2S2O3 (natrium thiosulfate). Banyakknya volume van Na2S2O3
(natrium thiosulfate) is gebruik as titrant gelykstaande aan I2 (jodium) en ekwivalente vlakke van die monster.
Standaard oplossing wat gebruik word in die iodometric metode is Na2S2O3 (natrium thiosulfate). Sout
word gewoonlik gevorm in die vorm van pentahydraat of
Na2S2O3.5H2OLarutan nie deur weeg direk distandaarisasi nie, maar moet
gestandaardiseerde met die standaard primer.Karena-Na2S2O3.5H2O
onbestendig in die langtermyn stoor.
Op
iodometric metode van die ondersoek moet gehou word stabiele pH
(waterstof pondus) Oplossing moet in stand gehou word op 1 pH van minder
as 8.Karena indien die pH is meer as 8 of in 1 alkaliese I2akan reageer
met natriumhidroksied (OH -) die volgende hyphoiodit Iodides en jodied
te vorm, en ontbind in. Iodidat wat kan oksideer thiosulfate die reaksie sulfat.Sehingga nie kwantitatiewe uit te voer.
Hierdie
metode maak gebruik van 'n aanwyser op AMYLUM 1% AMYLUM eiendomme wat
moeilik om te los op in water en onstabiel in die water skorsing te vorm
komplekse verbindings swak oplosbaar in water wanneer met
iodium.Sehingga penanbahan AMYLUM reageer as aanwysers moet nie bygevoeg
word nie aan die begin reaksi.penambahan AMYLUM. as 'n aanduiding gegee moet word na die eindpunt-titrasie (in die tyd van die bleekgeel oplossing).
Titrasies
einde punt is gemerk met die blou kleur verandering in 1 duidelike
oplossing (van blou blou hilang.Jadi byvoeging van stysel word uitgevoer
uit as dit nader aan die titrasie einde punt is so dat stysel maak nie
draai as dit sal veroorsaak dat die stysel jodium getitreer moeilik om
terug te keer na die oorspronklike saamgestelde. Proses van titrasie moet
word so gou as moontlik gedoen word, dit is as gevolg van die maklike
aard van I2 menuap. Op die titrasie einde punt wat is gebind jodium ook
reageer met die titrant verloor so skielik verdwyn en die blou kleur
verandering baie duidelik. Die gebruik van hierdie aanwyser die
oplossing kleur veranderinge wat plaasvind te verduidelik by die
eindpunt .
titrasie sensitiwiteit van die kleur hang af van die oplosmiddel
gebruik jodium-stysel kompleks het 1 klein oplosbaarheid in die water,
so dit is in die algemeen bygevoeg by die titrasie einde punt, As 'n
oplossing van jodium in Ki in die neutrale atmosfeer word getitreer met
natrium thiosulfate, dan. nie.
- + I3-3i-+ 2S2O32 S4O62
S2O32-+ I3-2i-+-S2O3I
2S2O3I-+ I-+ I3-S4O62-
S2O3I-+-S4O62 S2O32-+ I-
Kan
Natrium thiosulfate (Na2S2O3.5H2O) maklik in 'n hoë staat van reinheid,
maar daar is altyd 'n bietjie onseker oor die presiese water-inhoud,
het veral karenaNa2S2O3.5H2O flouresen of verrottende eienskappe van die
sout-gekraak en onbestendig in die langtermyn stoor. Daarom is hierdie stowwe is nie in aanmerking kom om te dien as die primêre standaard voorraad oplossings. Natrium thiosulfate (Na2S2O3.5H2O) is 'n reduseermiddel, met die volgende vergelyking:
2S2O32-S4O62-+ 2e-
Standaardisering
van natrium thiosulfate (Na2S2O3.5H2O) kan gedoen word deur gebruik te
maak van kaliumjodaat, kalium chromaat, koper en jodium as die primêre
standaard oplossing, of met die kaliumpermanganaat of cerium (IV)
sulfaat as die sekondêre standaard oplossing. Maar
in hierdie eksperiment is die verbinding wat gebruik word in die proses
van standaardisering van natrium thiosulfate (Na2S2O3.5H2O) is
kaliumjodaat (KIO3) standaarde.
Die
oplossing van natrium thiosulfate (Na2S2O3.5H2O) voordat dit gebruik
word as 'n standaard oplossing in die iodometric proses moet wees
gestandaardiseerde vooraf deur kaliumjodaat (KIO3) wat die primêre
standaard is. Die
oplossing van kaliumjodaat (KIO3) iniharus met gekonsentreerde
swaelsuur bygevoeg, die kleur van die oplossing duidelik geword. En ná die toevoeging van die kaliumjodied (I2), word die oplossing donkerbruin. Funksie
van die toevoeging van gekonsentreerde swaelsuur (H2SO4 PA) in die
oplossing is om die suur te gee, omdat die oplossing wat bestaan uit
kaliumjodaat (KIO3) en klium jodied (KI) is in neutraal of het 'n lae
suur.
Sy reaksie is soos volg:
IO3-+ 5i-+ 6H + → 3I2 + 3H2O
Bepaling van die vlakke van Cu2 + deur Standard Na2S2O3 oplossing
In
die bepaling van Cu deur standaard Na2S2O3 oplossing sal 'n verandering
in die kleur van die oplossing voor die titrasie eindpunt te wees. Suiwer
koper kan gebruik word as 'n primêre standaard vir thiosulfate en
natrium thiosulfate moet aanbeveel word indien dit gebruik om koper te
bepaal. Standard paar potensiaal Cu (II) - Cu (I) is 0,15 V, en dus jodium is 'n beter oksideermiddel as die ioon Cu (II). Maar wanneer die jodied ioon na 'n oplossing van Cu (II) gevoeg word, sal presipitaat gevorm Cu (I).
2Cu2 + + 4I-2CuI (s) + I2
Die
bepaling van Cu2 + in 'n oplossing met behulp van 'n oplossing van
natrium thiosulfate uitgevoer verdun 5 ml voorbeeld van die sout 100 ml
en 10 ml van verwatering is te word bygevoeg tot 1 oplossing van KI 10%,
en Titel van standaard oplossing van natrium thiosulfate tot die
oplossing van die oorspronklike donker bruin tot 'n oplossing van 'n liggeel. Toe
het die oplossing is bygevoeg met 2 ml van 1% styseloplossing produseer
aanvanklik liggeel tot donker blou, byvoeging van 1% stysel aanwyser is
bedoel om die kleur veranderinge wat plaasvind in die oplossing te
verduidelik nie. dan is die oplossing is terug getitreer met natrium thiosulfate oplossing totdat die blou kleur van die oplossing. Die
voorkoms van die reaksie Om verder te verduidelik, is bygevoeg om 'n
oplossing van I2 met stysel amilum.Bertemunya dit sal veroorsaak dat 'n
blou-gekleurde oplossing kehitaman.Selanjutnya titrasie voortgesit word
totdat die blou kleur verdwyn en 'n bewolkte wit.
I2 + I2-stysel stysel
2S2O32 + I2-stysel-2i + S4O6 + stysel-
Dinge
om te oorweeg na die toevoeging van stysel is die aard van die
adsorpsie op die oppervlak van die afsetting van koper (I) jodied. Hierdie
eienskappe lei tot die opname van jodium en waar jodium is verwyder
deur titrasie, sal die titrasie eindpunt te vinnig bereik word. Daarom
is voor die titrasie eindpunt bereik, wanneer die kleur van die
oplossing word getitreer met Na2S2O3akan verander van blou skoon te
maak, die byvoeging van kaliumthiocyanaat KCNS.
Verwysings
PRAKTEK IODOMETRI penentuan kadar CuSO4