Titrasi: Perbedaan revisi

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'''Titrasi''' merupakan metode analisa kimia secara kuantitatif yang biasa digunakan dalam laboratorium untuk menentukan konsentrasi dari [[reaktan]]. Karena pengukuran volum memainkan peranan penting dalam titrasi, maka teknik ini juga dikenali dengan analisa volumetrik.
A [[reagent]], called the ''titrant'' or ''titrator'',[1]<ref>Compendium for basal practice in biochemistry, 2008 ed.. Aarhus University</ref> of a known concentration (a [[standard solution]]) and [[volume]] is used to react with a solution of the [[analyte]] or ''titrand'',[2]<ref>{{cite web|url=http://www.answers.com/topic/titrand \ publisher=Sci-Tech Dictionary|title=titrand}}</ref> whose concentration is not known. Using a calibrated [[burette]] to add the titrant, it is possible to determine the exact amount that has been consumed when the ''endpoint'' is 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—thepoint]]&mdash;the volume of added titrant at which the number of [[Mole (unit)|moles]] of titrant 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 often when the solution takes on a persisting solid color as in the pink of phenolphthalein [[pH indicator|indicator]]. 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 color). In simple [[acid-base titrationstitration]]s a pH indicator may be used, such as [[phenolphthalein]], 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 the products are strongly colored and can serve as the "indicator". For example, a [[redox titration]] using [[potassium permanganate]] (pink/purple) as the titrant does not require an indicator. When the titrant is reduced, it turns colorless. After the equivalence point, there is excess titrant present. The equivalence point is identified from the first faint persisting pink color (due to an excess of permanganate) 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 ''endpoint'' can change the pH significantly—leadingsignificantly&mdash;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 the titration. This error is referred to as an indicator error, and it is indeterminate.