2nd Exam - TITRATION METHOD Flashcards
based upon measuring the amount of reagent of known concentration that is consumed by the analyte
are capable of rapid and convenient analyte determinations with high accuracy and precision
Titrimetric Methods of Analysis
involves measuring the volume of a
solution of known concentration that is needed to react
essentially and completely with the analyte
Volumetric Titrimetry
differs only in that the mass of the
reagent is measured instead of its volume
Gravimetric Titrimetry
the reagent is a constant direct
electric current of known magnitude that is directly or
indirectly reacts with the analyte here, the time required to
complete the electrochemical reaction is measured
Coulometric Titrimetry
most common reaction types in titrations
acid-base, redox, precipitation and complex reactions.
T or F? The concentration of the titrant solution, CT, must be known accurately
T
The ______ solution must be standardized either by preparing it using a primary standard or, more commonly, titrating it against a solution prepared with a primary standard
titrant
is a reagent of exactly known
concentration that is used in a titrimetric analysis
standard solution
is an ultrapure compound that serves as the reference material for a titrimetric method of analysis
primary standard
Titration solution requirements
- high purity
- stability towards air
- absence of water of hydration
- ready availability at modest cost
- reasonable solubility in the titration medium
- reasonably large molar mass so that the relative error associated with weighing the standard is minimized
is a compound whose purity has been
established by chemical analysis and that serves as the
reference material for a titrimetric method of analysis
secondary standard
is a process in which a standard reagent is added
to a solution of an analyte until the reaction between the analyte and the reagent is judged to be complete
titration
is a process in which the excess of a standard
solution used to consume an analyte is determined by titration with a second standard solution
are often required when the rate of reaction between the analyte and reagent is slow or when the standard solution lacks stability
back-titration
is a process in which the concentration of a
volumetric solution (secondary standard) is determined by using it to titrate a known mass of a primary standard or an exactly known volume of another secondary standard solution
standardization
is the point in a titration when the amount of
added standard reagent is exactly equivalent to the amount of analyte
equivalence point
is the point in a titration when a physical change
occurs that is associated with the condition of chemical equivalence
end point
The difference in volume or mass between the equivalence point and the end point is the
titration error
Et= Vep-Veq
are added to the analyte solution to
produce an observable physical change the end
point at or near the equivalence point change
in color or appearance or disappearance of
turbidity
indicators
here, a carefully weighed quantity
of a primary standard is dissolved in a suitable
solvent and diluted to an exactly known volume in a
volumetric flask
direct method
In standardization, the ______ to be
standardized is used to titrate:
- a weighed quantity of primary standard,
- a weighed quantity of secondary standard,
- a measured volume of another standard solution
titrant
is based on the neutralization
reaction between the analyte and an acidic or basic
titrant These most commonly use a pH indicator, a pH
meter, or a conductance meter to determine the
endpoint
acid-base titration
is based on an oxidation reduction
reaction between the analyte and titrant These most
commonly use a potentiometer or a redox indicator to
determine the endpoint Frequently either the reactants
or the titrant have a color intense enough that an
additional indicator is not needed
redox titration
is based on the formation of a
complex between the analyte and the titrant
Complexometric titration
is very commonly used to titrate metal ions in
solution Requires specialized indicators that form weaker complexes with the metal A
chelating agent EDTA
common example of EDTA (for the titration of calcium and magnesium ions)
Eriochrome Black T
The titrant forms an insoluble product with the analyte Example is the titration of chloride ion with silver nitrate solution to form silver chloride precipitate Indicators can be used to detect the end point or potential of the solution can be monitored electrically
Precipitation titration
small amount of sample used for analysis
aliquot
of a solution is the mass (in mg) of a substance
that is chemically equivalent to 1 mL of the solution.
titer
To analyze a sample of unknown purity the analyst
weighs accurately a portion of the sample, dissolves
it appropriately, and titrates it with a standard
solution.
percent purity
for nitrogen determination
Kjeldahl method
