TITRATIONS IN ANALYTICAL CHEMISTRY Flashcards
are widely used in analytical chemistry to determine acids, bases, oxidants, reductants, metal ions, proteins, and many other species.
Titrations
titrations are based on a reaction between the analyte and a standard reagent known as the ____
titrant
are based on determining the quantity of a reagent of known concentration that is required to react completely with the analyte. The reagent may be a standard solution of a chemical or an electric current of known magnitude.
Titration Methods
3 Methods for Titration:
Volumetric Titration
Gravimetric Titration
Coulometric Titration
involves measuring the volume of a solution of known concentration that is needed to react completely with the analyte
Volumetric Titration -
the mass of the reagent is measured instead of its volume
Gravimetric Titration
the quantity of charge required to complete a reaction with the analyte is the measured quantity
Coulometric Titration
is a reagent of known concentration that is used to carry out a volumetric titration
Standard Solution
a process in which the excess of a standard solution used to consume an analyte is determined by titration with a second standard solution.
Back Titrations
is the point in a titration when the amount of added standard reagent is 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
Titration Error (Et)
ctual volume to reach end point
Vep
theoretical volume to reach equivalence point
Veq
compounds that allow us to detect end point of titrations
Indicators
weak organic acid or a weak organic base whose undissociated form differs in color from its conjugate base or its conjugate acid form
Acid-base indicators
oxidizing agents or reducing agent and signals the end point of redox solution.
Redox Indicator
organic dyes, colored complex metal ions, must bind less strongly by metal ions than the complex agent does.
Metal- Ion indicators
is an ultrapure compound that serves as the reference material for titration or for another type of quantitative analysis
Primary Standards
is a compound whose purity has been determined by chemical analysis. The secondary standard serves as the working standard material for titrations and for many other analyses
Secondary Standard
Methods to establish concentration of solution:
Direct Method\
Standardization
VOLUMETRIC CALCULATIONS
Molarity/ Normality
Equivalence weight
Molality
number of gram or mole equivalents of solute present in one liter of solution.
Normality
gram atomic weight divided by its valence.
Equivalent Weight
involves using relationship between reactants/products in a chemical reaction to determine desired quantitative data; balancing of reactions
Stoichiometric Calculations
differ from their volumetric counterparts in that the mass of the titrant is measured rather than the volume.
gravimetric titrations
are widely used to determine the amounts of acids and bases.
Neutralization titrations
Most Common Acid/ Base Indicators:
titration of strong acid: such as hydrochloric or sulfuric acid
titration of a weak acid: such as acetic or lactic acid
titration of weak bases: such as sodium cyanide or sodium salicylate
such as hydrochloric or sulfuric acid
titration of strong acid:
such as acetic or lactic acid
titration of a weak acid:
such as sodium cyanide or sodium salicylate
titration of weak bases:
2 TYPES OF TITRATION ERROR
Determinate Error
Indeterminate Error
occurs when the pH at which the indicator change color differs from the pH at the equivalence point.
Determinate Error
depends on the change in pH.
originates from the limited ability of the human eye to the indeterminate color of the indicator.
Indeterminate Error
Variables that influence the behavior of indicator:
Temperature
The ionic strength of medium
Presence of organic solvents & colloidal particles
