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9.S: Titrimetric Methods (Summary)

  • Page ID
    70473
  • In a titrimetric method of analysis, the volume of titrant reacting stoichiometrically with a titrand provides quantitative information about the amount of analyte in a sample. The volume of titrant corresponding to this stoichiometric reaction is called the equivalence point. Experimentally we determine the titration’s end point using an indicator that changes color near the equivalence point. Alternatively, we can locate the end point by continuously monitoring a property of the titrand’s solution—absorbance, potential, and temperature are typical examples—that changes as the titration progresses. In either case, an accurate result requires that the end point closely match the equivalence point. Knowing the shape of a titration curve is critical to evaluating the feasibility of a titrimetric method.

    Many titrations are direct, in which the analyte participates in the titration as the titrand or the titrant. Other titration strategies may be used when a direct reaction between the analyte and titrant is not feasible. In a back titration a reagent is added in excess to a solution containing the analyte. When the reaction between the reagent and the analyte is complete, the amount of excess reagent is determined by a titration. In a displacement titration the analyte displaces a reagent, usually from a complex, and the amount of displaced reagent is determined by an appropriate titration.

    Titrimetric methods have been developed using acid–base, complexation, redox, and precipitation reactions. Acid–base titrations use a strong acid or a strong base as a titrant. The most common titrant for a complexation titration is EDTA. Because of their stability against air oxidation, most redox titrations use an oxidizing agent as a titrant. Titrations with reducing agents also are possible. Precipitation titrations often involve Ag+ as either the analyte or titrant.

    9.6.1 Key Terms

    acid–base titration
    acidity
    alkalinity
    argentometric titration
    asymmetric equivalence point
    auxiliary complexing agent
    auxiliary oxidizing agent
    auxiliary reducing agent
    back titration
    buret
    complexation titration
    conditional formation constant
    direct titration
    displacement titration
    end point
    equivalence point
    Fajans method
    formal potential
    Gran plot
    indicator
    Jones reductor
    Kjeldahl analysis
    leveling
    metallochromic indicator
    Mohr method
    potentiometric titration
    precipitation titration
    redox indicator
    redox titration
    spectrophotometric titration
    symmetric equivalence point
    thermometric titration
    titrand
    titrant
    titration curve
    titration error
    titrimetry
    Volhard method
    Walden reductor
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    References

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