Acid-base titration
Acid-Base titrations are usually used to find the the
amount of a known acidic or basic substance through acid base reactions. The
analyte (titrand) is the solution with an unknown molarity. The reagent
(titrant) is the solution with a known molarity that will react with the
analyte.
Definitions
Acid-base titration : Determines the concentration of an acid or base by exactly
neutralizing it with an acid or base of known concentration.
Equivalence point:
The point
at which an added titrant's moles are stoichiometrically equal to the moles of
acid/base in the sample; the smallest amount of titrant needed to fully
neutralize or react with the analyte.
Titrant: The standardized (known) solution (either an acid
or a base) that is added during titration.
Analyte: The unknown solution whose concentration is being
determined in the titration.
Procedure
An acid-base titration is an experimental procedure used to
determine the unknown concentration of an acid or base by precisely
neutralizing it with an acid or base of known concentration. This lets us
quantitatively analyze the concentration of the unknown solution. Acid-base
titrations can also be used to quantify the purity of chemicals.
Alkalimetry, or alkimetry, is the specialized analytic use
of acid-base titration to determine the concentration of a basic (alkaline)
substance; acidimetry, or acidometry, is the same concept applied to an acidic
substance.
The solution in the flask contains an unknown number of
equivalents of base (or acid). The burette is calibrated to show volume to the
nearest 0.001 cm3. It is filled with a solution of strong acid (or base) of
known concentration. Small increments are added from the burette until, at the
end point, one drop changes the indicator color permanently. (An indication of
the approaching equivalence point is the appearance, and disappearance after
stirring, of the color that the indicator assumes beyond neutralization.) At
the equivalence point, the total amount of acid (or base) is recorded from the
burette readings. The number of equivalents of acid and base must be equal at
the equivalence point.
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