Titration_Level II_12 Juin 2008

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Titration

Titration setup: the titrant drops from theburette into the analyte solution in theflask. Anindicator present then changes color permanently at theendpoint.

Titration is a common laboratory method of quantitative/chemical analysisthat can be

used to determine the concentrationof a known reactant. Because volume measurements

play a key role in titration, it is also known as volumetric analysis. A reagent, called thetitrant, of known concentration (a standard solution) and volume is used to react with a

solution of the analyte, whose concentration is not known in advance. Using a calibrated

buretteto add the titrant, it is possible to determine the exact amount that has beenconsumed when the endpointis reached. The endpoint is the point at which the titration is

complete, as determined by an indicator (see below). This is ideally the same volume as

the equivalence point- the volume of added titrant at which the number ofmoles oftitrant is equal to the number of moles of analyte, or some multiple thereof (as in

polyprotic acids). In the classic strong acid-strong base titration, the endpoint of a

titration is the point at which the pH of the reactant is just about equal to 7, and oftenwhen the solution permanently changes color due to anindicator. There are however

many different types of titrations (see below).

Many methods can be used to indicate the endpoint of a reaction; titrations often use

visual indicators (the reactant mixture changes colour). In simple acid-base titrations apH indicator may be used, such asphenolphthalein, which becomes pink when a certain

pH (about 8.2) is reached or exceeded. Another example is methyl orange, which is red in

acids and yellow in alkali solutions.

Not every titration requires an indicator. In some cases, either the reactants or theproducts are strongly coloured and can serve as the "indicator". For example, an

oxidation-reduction titration usingpotassium permanganate (pink/purple) as the titrant
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does not require an indicator. When the titrant is reduced, it turns colourless. After the

equivalence point, there is excess titrant present. The equivalence point is identified from

the first faint pink color that persists in the solution being titrated.

Due to the logarithmic nature of the pH curve, the transitions are, in general, extremely

sharp; and, thus, a single drop of titrant just before the endpointcan change the pHsignificantly leading to an immediate colour change in the indicator. There is a slight

difference between the change in indicator color and the actual equivalence point of thetitration. This error is referred to as an indicator error, and it is indeterminate.

History and etymology

The word "titration" comes from the Latin word titalus, meaning inscription or title. TheFrench word titre, also from this origin, means rank. Titration, by definition, is the

determination of rank or concentration of a solution with respect to water with a pH of 7

(which is the pH of pure water).

The origins of volumetric analysis are in late-18th-century French chemistry. FrancoisAntoine Henri Descroizilles developed the first burette (which looked more like a

graduated cylinder) in 1791. Joseph Louis Gay-Lussacdeveloped an improved version of

the burette that included a side arm, and coined the terms "pipette" and "burette" in an

1824 paper on the standardization of indigo solutions. A major breakthrough in themethodology and popularization of volumetric analysis was due to Karl Friedrich Mohr,

who redesigned the burette by placing a clamp and a tip at the bottom, and wrote the first

textbook on the topic,Lehrbuch der chemisch-analytischen Titrirmethode (Textbook ofanalytical-chemical titration methods), published in 1855.[1]

Preparing a sample for titration

In a titration, both titrant and analyte are required to beaqueous, or in a solution form. If

the sample is not a liquid or solution, the samples must be dissolved. If the analyte is veryconcentrated in the sample, it might be useful to dilute the sample.

Although the vast majority of titrations are carried out in aqueous solution, other solvents

such as glacial acetic acid orethanol(inpetrochemistry) are used for special purposes.

A measured amount of the sample can be given in the flask and then be dissolved or

diluted. The mathematical result of the titration can be calculated directly with themeasured amount. Sometimes the sample is dissolved or diluted beforehand, and a

measured amount of the solution is used for titration. In this case the dissolving or

diluting must be done accurately with a known coefficientbecause the mathematicalresult of the titration must be multiplied with this factor.

Many titrations require buffering to maintain a certainpHfor the reaction. Therefore,

buffer solutions are added to the reactant solution in the flask.
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Some titrations require "masking" of a certain ion. This can be necessary when two

reactants in the sample would react with the titrant and only one of them must be

analysed, or when the reaction would be disturbed or inhibited by this ion. In this caseanother solution is added to the sample, which "masks" the unwanted ion (for instance by

a weak binding with it or even forming a solid insoluble substance with it).

Some redox reactions may require heating the solution with the sample and titration

while the solution is still hot (to increase thereaction rate).

Procedure

A typical titration begins with abeakerorErlenmeyer flaskcontaining a precise volume

of the reactant and a small amount of indicator, placed underneath aburettecontainingthe reagent. By controlling the amount of reagent added to the reactant, it is possible to

detect the point at which the indicator changes colour. As long as the indicator has been

chosen correctly, this should also be the point where the reactant and reagent neutralise

each other, and, by reading the scale on the burette, the volume of reagent can bemeasured.

As the concentration of the reagent is known, the number of moles of reagent can be

calculated (since concentration = moles / volume). Then, from the chemical equation

involving the two substances, the number of moles present in the reactant can be found.Finally, by dividing the number of moles of reactant by its volume, the concentration is

calculated.

Titration curves

A typical titration curve of a diprotic acid,oxalic acid, titrated with a strong base, sodium

hydroxide. Each of the two equivalence points are visible

Titrations are often recorded on titration curves, whose compositions are generally

identical: the independent variable is the volume of the titrant, while the dependentvariable is the pH of the solution (which changes depending on the composition of the

two solutions).
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The equivalence point is a significant point on the graph (the point at which all of the

starting solution, usually an acid, has been neutralized by the titrant, usually a base). It

can be calculated precisely by finding the second derivative of the titration curve andcomputing thepoints of inflection(where the graph changes concavity); however, in

most cases, simple visual inspection of the curve will suffice (in the curve given to the

right, both equivalence points are visible, after roughly 15 and 30 mL ofNaOH solutionhas been titrated into the oxalic acidsolution.)

To calculate the pKa values, one must find the volume at the half-equivalence point, that

is where half the amount of titrant has been added to form the next compound (here,

sodium hydrogen oxalate, then disodium oxalate). Halfway between each equivalencepoint, at 7.5 mL and 22.5 mL, the pH observed was about 1.5 and 4, giving the pKa

values.

In monoprotic acids, the point halfway between the beginning of the curve (before any

titrant has been added) and the equivalence point is significant: at that point, the

concentrations of the two species (the acid and conjugate base) are equal. Therefore, theHenderson-Hasselbalch equationcan be solved in this manner:

Therefore, one can easily find the acid dissociation constant of the monoprotic acid by

finding the pH of the point halfway between the beginning of the curve and theequivalence point, and solving the simplified equation. In the case of the sample curve,

theKa would be approximately 1.7810-5 from visual inspection (the actualKa2 is 1.710

-

5)

Forpolyprotic acids, calculating the acid dissociation constants is only marginally moredifficult: the first acid dissociation constant can be calculated the same way as it would

be calculated in a monoprotic acid. The second acid dissociation constant, however, is the

point halfway between the first equivalence point and the second equivalence point (andso on for acids that release more than two protons, such asphosphoric acid).
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Types of titrations

Titrations can be classified by the type of reaction. Different types of titration reaction

include:

Acid-base titrations are based on the neutralization reaction between the analyteand an acidic or basic titrant. These most commonly use a pH indicator, a pH

meter, or a conductance meter to determine the endpoint.

Redox titrations are based on an oxidation-reduction reaction between the analyteand titrant. These most commonly use a potentiometer or a redox indicator to

determine the endpoint. Frequently either the reactants or the titrant have a colour

intense enough that an additional indicator is not needed.

Complexometric titrations are based on the formation of a complex between the

analyte and the titrant. The chelating agentEDTA is very commonly used to

titrate metal ions in solution. These titrations generally require specializedindicatorsthat form weaker complexes with the analyte. A common example is

Eriochrome Black T for the titration ofcalcium and magnesiumions. A form of titration can also be used to determine the concentration of a virus or

bacterium. The original sample is diluted (in some fixed ratio, such as 1:1, 1:2,1:4, 1:8, etc.) until the last dilution does not give a positive test for the presence of

the virus. This value, the titre, may be based on TCID50,EID50,ELD50, LD50 or

pfu. This procedure is more commonly known as an assay.

Measuring the endpoint of a titration

Different methods to determine the endpoint include:

pH indicator: This is a substance that changes colour in response to a chemical

change. An acid-base indicator (e.g.,phenolphthalein) changes colour dependingon thepH.Redox indicators are also frequently used. A drop of indicator solution

is added to the titration at the start; when the colour changes the endpoint has

been reached.

Apotentiometercan also be used. This is an instrument that measures theelectrode potential of the solution. These are used for titrations based on a redox

reaction; the potential of the working electrode will suddenly change as the

endpoint is reached.

pH meter: This is a potentiometer that uses an electrode whose potential depends

on the amount of H+ ion present in the solution. (This is an example of anion-

selective electrode. This allows the pH of the solution to be measured throughoutthe titration. At the endpoint, there will be a sudden change in the measured pH. It

can be more accurate than the indicator method, and is very easily automated.

Conductance: Theconductivity of a solution depends on the ions that are presentin it. During many titrations, the conductivity changes significantly. (For instance,

during an acid-base titration, the H+ and OH- ions react to form neutral H2O. This

changes the conductivity of the solution.) The total conductance of the solution
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depends also on the other ions present in the solution (such as counter ions). Not

all ions contribute equally to the conductivity; this also depends on the mobility of

each ion and on the total concentration of ions (ionic strength). Thus, predictingthe change in conductivity is harder than measuring it.

Colour change: In some reactions, the solution changes colour without any added

indicator. This is often seen in redox titrations, for instance, when the differentoxidation states of the product and reactant produce different colours.

Precipitation: If the reaction forms a solid, then aprecipitatewill form during the

titration. A classic example is the reaction between Ag+ and Cl- to form the veryinsoluble salt AgCl. This usually makes it difficult to determine the endpoint

precisely. As a result, precipitation titrations often have to be done as "back"

titrations (see below).

An isothermal titration calorimeteruses the heat produced or consumed by thereaction to determine the endpoint. This is important inbiochemical titrations,

such as the determination of how substratesbind to enzymes.

Thermometric titrimetry is an extraordinarily versatile technique. This is

differentiated from calorimetric titrimetry by the fact that the heat of the reaction(as indicated by temperature rise or fall) is not used to determine the amount of

analyte in the sample solution. Instead, the endpoint is determined by the rate oftemperature change.

Spectroscopy can be used to measure the absorption of light by the solution

during the titration, if the spectrum of the reactant, titrant or product is known.The relative amounts of the product and reactant can be used to determine the

endpoint.

Back Titration

The termback titrationis used when a titration is done "backwards": instead of titratingthe original analyte, one adds a known excess of a standard reagent to the solution, then

titrates the excess. A back titration is useful if the endpoint of the reverse titration iseasier to identify than the endpoint of the normal titration. They are also useful if the

reaction between the analyte and the titrant is very slow.

Particular uses

Titrations in thepetrochemical orfood industry to define oils, fats or biodieseland similar substances. An example procedure for all three can be found here: [1].

o Acid number: an acid-base titration with colour indicator is used to

determine the free fatty acidcontent. See also:pH of fatty acids.o Iodine number: a redox titration with colour indication, which indicates

the amount ofunsaturated fatty acids.

o Saponification value: an acid-base back titration with colour indicator or

potentiometric to get a hint about the average chain length of fatty acids in

a fat.
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References

1. ^ Louis Rosenfeld.Four Centuries of Clinical Chemistry. CRC Press, 1999, p. 72-75.
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Titrage

Montage d'un titrage

La titrimtrie ou titrage est une technique dedosage utilise en chimie analytique afin

de dterminer la concentration d'une espce chimique en solution (ou titre d'une solution).

La mthode de titrage la plus utilise est la volumtrie ou titrage volumtrique. Elle

consiste utiliser une solution de concentration connue (appele titrant) afin deneutraliser une espce contenue dans la solution inconnue.

Les titrages volumtriques les plus rpandus sont les titrages acide-base : L'oprateur fait

couler goutte goutte un acide dans un volume dtermin de base. Ainsi les ractifs

ragissent mol mol. Le titrage base-acide est aussi possible.

Le point de neutralisation est connu grce un indicateur color ajout dans la solution

inconnue (Cet indicateur change de couleur au moment de la neutralisation) ou grce

une variation du potentiel ou dupH (mesur au moyen d'une lectrode trempant dans lasolution inconnue).
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Matriel ncessaire [modifier]

Montage pour faire un titrage. La burette contient une solution titrante, et l'erlen lasolution titrer

On utilise en gnral une burette gradue quand le titrage est manuel ou un titrimtre

automatique quand on souhaite amliorer la rptabilit et la traabilit. Le volume de

l'chantillon est prlev au moyen d'une pipette de volume dtermin et est plac dans unerlenmeyer. Laburette contient toujours la solution de ractif titrante dont on connat la

concentration. La burette donne le volume vers de solution titrante et donc nous donnera

le point l'quivalence. La solution doser sera toujours dans un becher ou autre

rcipient propre, elle sera en volumeexactement connu.

Titrage en solution aqueuse [modifier]

Pour raliser un titrage, on ralise une raction chimique o l'espce en solution ragitavec une autre substance. L'espce doser est appele ractif titr et la substance ajoute

est appele ractif titrant

Il est possible de raliser un titrageconductimtrique (pour une raction acido-basique),

un titrage colorimtrique, un titragepH-mtrique, ...
http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=1http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=1http://fr.wikipedia.org/wiki/Erlenmeyer_(fiole)http://fr.wikipedia.org/wiki/Burettehttp://fr.wikipedia.org/wiki/Burettehttp://fr.wikipedia.org/wiki/Concentration_molairehttp://fr.wikipedia.org/wiki/Concentration_molairehttp://fr.wikipedia.org/wiki/Volumehttp://fr.wikipedia.org/wiki/Volumehttp://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=2http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=2http://fr.wikipedia.org/wiki/Conductim%C3%A9triehttp://fr.wikipedia.org/wiki/Conductim%C3%A9triehttp://fr.wikipedia.org/wiki/R%C3%A9action_acido-basiquehttp://fr.wikipedia.org/wiki/Titrage_colorim%C3%A9triquehttp://fr.wikipedia.org/wiki/Titrage_colorim%C3%A9triquehttp://fr.wikipedia.org/wiki/Potentiel_hydrog%C3%A8nehttp://fr.wikipedia.org/wiki/Image:Titration.pnghttp://fr.wikipedia.org/wiki/Image:Titration.pnghttp://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=1http://fr.wikipedia.org/wiki/Erlenmeyer_(fiole)http://fr.wikipedia.org/wiki/Burettehttp://fr.wikipedia.org/wiki/Concentration_molairehttp://fr.wikipedia.org/wiki/Volumehttp://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=2http://fr.wikipedia.org/wiki/Conductim%C3%A9triehttp://fr.wikipedia.org/wiki/R%C3%A9action_acido-basiquehttp://fr.wikipedia.org/wiki/Titrage_colorim%C3%A9triquehttp://fr.wikipedia.org/wiki/Potentiel_hydrog%C3%A8ne


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Les titrages pH-mtrique [modifier]

Dosage d'un acide fort par une base faible en prsence d'un indicateur color.

Ce type de titrage est ralisable uniquement avec des acides et des bases, faible ou fort, etsous prsence d'unPH-mtre ou d'un indicateur de pHcolore.

Titrage d'un acide fort par une base forte [modifier]

En solution, les acides forts comme l'acide chlorhydrique sont totalement dissocis et

donnent des ions . De mme, lesbases fortes se dissocient totalement pour librer

des ions . Les ions et ragissent de la faon suivante:

(Voici l'quation gnrale de neutralisation)

Au volume l'quivalence tous les ionsH3O+ et OH ont ragit, la seule raction quise produit est celle de l'autoprotolyse de l'eau. Le pH est alors gal 7. L'quivalence est

indique soit par un indicateur de pH, soit indirectement par une courbe reprsentant le

pH en fonction du volume de base vers. Vous devez pour cela relever les valeurs du PH-mtre pour chaque mL de solution verse. Quand le pH commence augmenter de faon

significative, versez alors 0,2 ml de solution entre chaque mesure de pH une fois que le

pH sera redevenu relativement stable reprenez une mesure de pH tous les ml En traant lacourbe du pH en fonction du volume de base verse, ont obtient la courbe reprsente

comme sur le dessin anim. Pour retrouver le volume l'quivalence, vous devez tracer

lestangentes aux deux points d'inflexion ( l o la courbe change de direction). Lestangentes doivent tre parallles. Tracer laperpendiculaire ces deux droites, puis

grce un compas, tracer la mdiatrice de la perpendiculaire. La mdiatrice doit treparallle aux tangentes . Le volume l'quivalence est l'endroit o la mdiatrice et la

courbe se rencontrent, pour un pH de 7 .

Les titrages colorimtriques [modifier]

Article dtaill : titrage colorimtrique.
http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=3http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=3http://fr.wikipedia.org/wiki/PH-m%C3%A8trehttp://fr.wikipedia.org/wiki/PH-m%C3%A8trehttp://fr.wikipedia.org/wiki/Indicateurhttp://fr.wikipedia.org/wiki/Indicateurhttp://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=4http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=4http://fr.wikipedia.org/wiki/Acidehttp://fr.wikipedia.org/wiki/Base_(chimie)http://fr.wikipedia.org/wiki/Autoprotolysehttp://fr.wikipedia.org/wiki/Autoprotolysehttp://fr.wikipedia.org/wiki/Indicateur_de_pHhttp://fr.wikipedia.org/wiki/Tangente_(g%C3%A9om%C3%A9trie)http://fr.wikipedia.org/wiki/Tangente_(g%C3%A9om%C3%A9trie)http://fr.wikipedia.org/wiki/Parall%C3%A9lisme_(g%C3%A9om%C3%A9trie)http://fr.wikipedia.org/wiki/Perpendiculairehttp://fr.wikipedia.org/wiki/M%C3%A9diatricehttp://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=5http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=5http://fr.wikipedia.org/wiki/Titrage_colorim%C3%A9triquehttp://fr.wikipedia.org/wiki/Image:Searchtool-80%25.pnghttp://fr.wikipedia.org/wiki/Image:Titolazione.gifhttp://fr.wikipedia.org/wiki/Image:Titolazione.gifhttp://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=3http://fr.wikipedia.org/wiki/PH-m%C3%A8trehttp://fr.wikipedia.org/wiki/Indicateurhttp://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=4http://fr.wikipedia.org/wiki/Acidehttp://fr.wikipedia.org/wiki/Base_(chimie)http://fr.wikipedia.org/wiki/Autoprotolysehttp://fr.wikipedia.org/wiki/Indicateur_de_pHhttp://fr.wikipedia.org/wiki/Tangente_(g%C3%A9om%C3%A9trie)http://fr.wikipedia.org/wiki/Parall%C3%A9lisme_(g%C3%A9om%C3%A9trie)http://fr.wikipedia.org/wiki/Perpendiculairehttp://fr.wikipedia.org/wiki/M%C3%A9diatricehttp://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=5http://fr.wikipedia.org/wiki/Titrage_colorim%C3%A9trique


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Les titrages conductimtriques [modifier]

Un titrage conductimtrique utilise la capacit des ions conduire le courant lectrique

dans un milieu aqueux, on mesure alors la conductance de la solution grce une

lectrode. Comme chaque ion conduit le courant diffremment, la conductance varie

pendant le dosage. Cette notion est directement lie avec la concentrationdes ionsprsents. Par exemple : L'ionH3O

+conduit mieux le courant que l'ion OH . Si vous

faites ragir les ionsH3O+

, la conductance de la solution va baisser car ces ions

disparaissent ( la concentration des ionsH3O+

diminue ) .Puis si vous continuez le

titrage au-del du point a l'quivalence, la conductance va monter, car les ions OH

seront de plus en plus nombreux,(la concentration des ions OH augmente). En relevantles valeurs indiques par le conductimtre, on peut tracer la droite de la conductance en

fonction du volume vers. Il se dessine alors deux droites adjacentes, en forme de V.Le

point adjacent indique le volume l'quivalence.

Calculs [modifier]

Le but d'un titrage est de trouver la concentration en un lment donn. Il existe pour cela

deux moyens possibles : par le calcul et par un tableau d'avancement. Dans les deux cas il

faut connatre l'quation bilan de la raction.

Mthode mathmatique [modifier]

A l'quivalence, il y a eu autant demoles de ractif A que de ractif B.

donc

Avec :

: concentration de la solution connue (titrant)

: volume de titrant coul en ml

: concentration de la solution inconnue

: volume d'chantillon utilis en ml

Cette formule est gnrale quels que soient les coefficients (ou nombres)stoechiomtriques.

En raisonnant avec les concentrations alors les coefficients stoechiomtriques

interviennent.
http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=6http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=6http://fr.wikipedia.org/wiki/Conductancehttp://fr.wikipedia.org/wiki/Concentration_molairehttp://fr.wikipedia.org/wiki/Concentration_molairehttp://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=7http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=7http://fr.wikipedia.org/wiki/Concentration_molairehttp://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=8http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=8http://fr.wikipedia.org/wiki/Mole_(unit%C3%A9)http://fr.wikipedia.org/wiki/Mole_(unit%C3%A9)http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=6http://fr.wikipedia.org/wiki/Conductancehttp://fr.wikipedia.org/wiki/Concentration_molairehttp://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=7http://fr.wikipedia.org/wiki/Concentration_molairehttp://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=8http://fr.wikipedia.org/wiki/Mole_(unit%C3%A9)


12/13

Tableau d'avancement [modifier]

Le bilan de la raction s'crit comme ceci :

Etat initial

Etat intermdiaire

Etat Final

Au dbut du titrage, (quand vous n'avez encore rien vers), vous n'avez que des ractifs et

aucun produit de raction. Au fur et mesure que votre raction se droule, une quantit

x de ractif disparat, alors qu'en mme temps une quantit x de produit apparat. C'estl'application de la loi de lavoisier. A la fin du titrage, c'est--dire quand un de vos ractifs

a totalement disparu (celui se trouvant dans votre erlen) vous avez atteint l'avancement

maximal, votre raction ne peut pas aller plus loin.

A ce moment l

donc

Ce tableau permet de comprendre ce qui ce passe pendant la raction et de ne pas vous

tromper avec les coefficients. En effet vous avez juste les reporter devant le X .Normalement quand vous avez de l'eau dans votre raction vous devez crire "en excs"

(vous avez toujours plus d'eau qu'il n'en faut pour que la raction se droule)

Calcul d'un excs [modifier]

Au dpart la solution titre est en excs. Aprs l'quivalence, c'est la solution titrante quiest en excs. Pour une raction acido-basique, l'acide est limitant au dbut et pour une

oxydo-rduction, c'est l'oxydant qui est limitant avant l'quivalence.

Un excs est une partie des ractifs qui ne ragit pas pendant une raction chimique et qui

se retrouve donc dans les produits de la raction. On peut doser l'excs de ractif avecune deuxime raction chimique : c'est un dosage en retour.

Rappels [modifier]
http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=9http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=9http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=10http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=10http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=11http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=11http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=9http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=10http://fr.wikipedia.org/w/index.php?title=Titrage&action=edit&section=11


13/13

Le nombre de mole correspond la quantit de matire d'une espce chimique.

La masse molaire d'un lment est la quantit de matire qu'il faut pour avoir

une mole de cet lement. Exemple : , il faut 12 grammes de carbone

pour avoir 1 mole.

La masse est la quantit de matire pese.

La concentration est la quantit de matire contenue dans un litre de solution.

Elle est exprime en mol/L ou en g/L.

C= n / Vou C= m / V
http://fr.wikipedia.org/wiki/Mole_(unit%C3%A9)http://fr.wikipedia.org/wiki/Masse_molairehttp://fr.wikipedia.org/wiki/Concentration_molairehttp://fr.wikipedia.org/wiki/Mole_(unit%C3%A9)http://fr.wikipedia.org/wiki/Masse_molairehttp://fr.wikipedia.org/wiki/Concentration_molaire

Titration_Level II_12 Juin 2008

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