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Analytical Chemistry
Chapter 0,1,3
34
Chemistry
Undergraduate 2
09/25/2011

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Term
decant
Definition
to pour liquid off a solid or perhaps a denser liquid. In which the denser phase is left behind
Term
analyte
Definition
the substance being measured
Term
slurry
Definition
suspension of a solid in a solvent
Term
supernatant liquid
Definition
liquid remaining above the solid after precipitation
Term
standard solution
Definition
solution whose composition is known by virtue of the way that it was made from reagent of a known purity or by virtue of its reaction with a known quantity of a standard reagent
Term
calibration curve
Definition
a graph showing the value of some property verse concentration of the analyte. when the corresponding property of an unknown is mesured it concentration can be determined on a graph
Term
interference
Definition
a phenomenon in which the presence of one substance changes the response in the analyis of another
Term
composite sample
Definition
a representative sample prepared from heterogeneous materia. If the material consist of distinct regionsthe composite is made of portions of each region with rellarive amounts proportionalto the size of each region
Term
electrolyte
Definition
a substance that dissociates into ions in solution
Term
strong electrolyte
Definition
mostly dissociates into ions in solution
Term
weak electrolye
Definition
partically dissociates into ions in solution
Term
gravimetric analyis
Definition
chemical analysis based on weighing a final product
Term
volumetric analyis
Definition
a techniquein which the volume of material needed to react with the analyte is measured
Term
titrant
Definition
the substance added to the anaylye in a titration
Term
titration
Definition
a procedure in which one substance is carefully added to another until complete reaction has occured. The quantitky of titrant required for complete reaction tells us how much analyte is present.
Term
titration curve
Definition
a graph showing how the concentration of a reactant or a physical property of the solution varies as one reactant is added to another
Term
primary standard
Definition
a reagent that is pure enough and stable enough to be used directly after weighing. the entire mass is considered to be pure reagent
Term
end point
Definition
point in a titration at which there is a sudden change in a physical propertysuch as indicator color, pH or absorbance used to measure equivalence point
Term
equilvance point
Definition
point in titration at which the quantity of the titrant is exactl sufficient for stoichiometric reaction with the analyte
Term
direct titration
Definition
one in which the analyte is treated with titrant and the volume of the titrant required for complete reaction is measured
Term
blank titration
Definition
one in which a solution containing all reagents except analyte is titrated. the volume of the titrant neeed in the blank titration should be subtracted from the volume needed to titrate the unknown
Term
back titration
Definition
one in which excess standard reagent is added to react with the analyte.then the excess reagent is titrated with a second reagent or with a standard solution of analyte
Term
reagent grade chemical
Definition
a high purity chemical generally suitable for use in quantitive analysis and meeting purity requirements set by organizations such as the american chemical society
Term
trace analysis
Definition
chemical analysis of very low levels of analyte typically ppm and lower
Term
absolute uncertainty
Definition
expresses the margin of uncertainty associated with a measurement
Term
relative uncertainty
Definition
compares the size of the absolute uncertianty with the size of its associated measurement
Term
accuracy
Definition
how close a measurement is to the true value
Term
precision
Definition
reproducablity
Term
random error/ indeterminate error
Definition
uncontrollable errors that can not be eliminated but can be reduced
Term
systimatic/determinate error
Definition
arises from flaw in equipement or design in experiment
Term
gaussian distribution
Definition
theoretical bell shaped distribution of measurements when all error is random the center of the curve is the mean and the width is characterized by standard deviation
Term
variances
Definition
the square of the standard deviation
Term
standard deviation
Definition
a statistic measuring of how closely data are clustered about the mean value.
Term
standard deviation of the mean
Definition
the standard deviation of a set of measurements divided by the square root of the number of measurements in the set
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