Titration

Only available on StudyMode
  • Download(s) : 89
  • Published : July 9, 2012
Open Document
Text Preview
-------------------------------------------------
Titration
From Wikipedia, the free encyclopedia
  (Redirected from Back titration)
Not to be confused with the mathematical notion of tetration. This article is about volumetric titration. For other uses, see Titration (disambiguation).

A Winkler titration to determine the concentration of dissolved oxygen in a water sample Titration, also known as titrimetry,[1] is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of an identified analyte. Because volume measurements play a key role in titration, it is also known as volumetric analysis. A reagent, called the titrant or titrator[2] is prepared as a standard solution. A known concentration and volume of titrant reacts with a solution of analyte or titrand[3] to determine concentration. Contents  [hide]  * 1 History and etymology * 2 Procedure * 2.1 Preparation techniques * 3 Titration curves * 4 Types of titrations * 4.1 Acid-base titration * 4.2 Redox titration * 4.3 Gas phase titration * 4.4 Complexometric titration * 4.5 Zeta potential titration * 4.6 Assay * 5 Measuring the endpoint of a titration * 5.1 Endpoint and equivalence point * 5.2 Back titration * 6 Particular uses * 7 See also * 8 References * 9 External links| -------------------------------------------------

[edit]History and etymology
The word "titration" comes from the Latin word titulus, meaning inscription or title. The French 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 (the pH of pure H2O under standard conditions).[4] Volumetric analysis originated in late 18th-century France. François-Antoine-Henri Descroizilles developed the first burette (which was similar to a graduated cylinder) in 1791.[5] Joseph Louis Gay-Lussac developed 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 the methodology 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 of analytical-chemical titration methods), published in 1855.[6] -------------------------------------------------

[edit]Procedure
A typical titration begins with a beaker or Erlenmeyer flask containing a precised volume of the titrand and a small amount of indicator placed underneath a calibrated burette orchemistry pipetting syringe containing the titrant. Small volumes of the titrant are then added to the titrand and indicator until the indicator changes, reflecting arrival at the endpoint of the titration. Depending on the endpoint desired, single drops or less than a single drop of the titrant can make the difference between a permanent and temporary change in the indicator. When the endpoint of the reaction is reached, the volume of reactant consumed is measured and used to calculate the concentration of analyte by

where Ca is the concentration of the analyte, typically in molarity; Ct is the concentration of the titrant, typically in molarity; Vt is the volume of the titrant used, typically in dm3; M is the mole ratio of the analyte and reactant from the balanced chemical equation; and Va is the volume of the analyte used, typically in dm3.[7] [edit]Preparation techniques

Typical titrations require titrant and analyte to be in a liquid (solution) form. Though solids are usually dissolved into an aqueous solution, other solvents such as glacial acetic acid orethanol are used for special purposes (as in petrochemistry).[8] Concentrated analytes are often diluted to improve accuracy. Many non-acid-base titrations...
tracking img