Analytical Chemistry Final Flashcards
a reagent of known concentration
that is used in a titrimetric analysis
standard solution
a process in which a standard reagent is
added to a solution of an analyte until the reaction
between the analyte and reagent is judged to be
complete
Titration
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-titration
the point in a titration when the amount
of added standard reagent is equivalent to the amount of analyte
equivalence point
the point in a titration when a physical change
occurs that is associated with the condition of chemical
equivalence
end point
often added to the analyte solution to give an
observable physical change (the end point) at or near the
equivalence point
Indicators
highly purified compound that serves
as a reference material in all volumetric and mass titrimetric
methods
primary standard
a carefully weighed
quantity of a primary standard is dissolved in a suitable
solvent and diluted to a known volume in a volumetric flask
direct method
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
the concentration of a volumetric
solution is determined by titrating it against a carefully
measured quantity of a primary or secondary standard or an
exactly known volume of another standard solution
standardization
the number of moles of
reagent contained in one liter of solution
Molar concentration
the number of equivalents of reagent in the
same volume
normal
concentration
the mass of
titrant is measured rather than the volume
Mass (weight) or gravimetric titrations
plots of a concentration related variable as a function of reagent volume
Titration curves
important observations are confined to a small region (typically ± 0.1 to ± 0.5 ml)
surrounding the equivalence point
sigmoidal curve,
measurements are made on both sides of but well away from the equivalence point
Linear segment curve
type offers the advantages of speed and
convenience
sigmoidal
a weak organic acid
or a weak organic base whose undissociated form differs in color from its conjugate form
acid/base indicator
a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid that resists changes in pH of a solution
buffer
a solution of a
conjugate acid / base pair that resists changes in pH
buffer solution
cause the most pronounced change in pH at the equivalence point
Strong acids and strong bases
donor species with at least one pair of unshared electrons
ligand
produced when a metal ion coordinates with two
or more donor groups of a single ligand to form a five- or six membered heterocyclic ring
chelate
A ligand that has a single donor group
unidentate
a ligand that has two groups available for covalent bonding
bidentate
Titrations with silver nitrate
argentometric titrations
The Mohr titration must be carried out at a pH of 7 to
10 because
chromate ion is the conjugate base of the weak chromic acid
in acidic solutions, where the pH is less than 7, the chromate ion concentration is
too low to produce the precipitate.
The most important application of the Volhard Method is for
indirect determination of halide ions
This reaction causes the end point to fade
precipitation titrations
indicators that respond to the analyte itself, whereas others are based on an added metal
ion
Direct titration
Spectrophotometric methods and Back-titration methods are examples of
Direct Titration
the study of how light interacts
with matter
Spectroscopy
the use of the absorption,
emission, or scattering of electromagnetic radiation by atoms or molecules (or atomic or molecular ions) to qualitatively or quantitatively
study the atoms or molecules, or to study physical processes
Spectroscopy
A transition from a lower level to a higher level with transfer of energy from the radiation field to the atom or molecule is called
absorption
A transition from a higher level to a lower level is called
emission
Redirection of light due to its interaction with matter is called
scattering
an energy wave that
is composed of an electric field component and a magnetic field component.
Electromagnetic radiation
Two concepts have
been used to describe EM
radiation:
the wave
model and the
particle model
The wave model characterizes EM radiation as
the
propagation of energy through transverse oscillations of the electric and magnetic fields
EM waves are measured by four parameters:
frequency, wavelength, polarization, and amplitude
the length of one complete oscillation or the distance between successive waves
Wavelength
the number of oscillations per sec. as measured in hertz
Frequency
the absolute strength of the EM
radiation as measured in volts per meter or amperes per meter
Amplitude
the relative orientation of the EM
radiation (horizontal, vertical, or circular)
Polarization
The unit is the reciprocal
centimeter (cm-1)
kaiser
The particle model proposes that EM radiation
consists of entities called
photons
photons can
possess only discrete amounts of energy aka
quanta
can only exist in motion, which,
for them, can only mean moving at the speed
of light
Photons
True or False? Photons can interact with other particles,
exchanging energy and momentum through
elastic and inelastic collisions
True
True or False? Higher-frequency EM radiation has higher
energy
True
relates the actual energy value of a quantum to
frequency in the equation
Planck’s constant
if the light frequency increases, the energy _____
increases
if the light wavelength increases, the energy ______
decreases
a quantum
mechanical phenomenon that results in the
emission of two photons in the same direction
with the same energy and spatial coherence
stimulated emission
light
amplification by stimulated emission of
radiation
laser
scattering,
reflection, and absorption are examples of
particle like behaviors
reflection,
refraction, transmission, diffraction, and
absorption are examples of
wavelike behaviors
If more than one material is involved in the passage of
EM radiation, the propagation direction is subject to
bending, which is called
refraction.
A reflecting medium that fails to produce an image is described as
diffuse
a medium that
loses an image during transmission is described
as
translucent
is nondirectional when the size of the
particles is on the order of the radiation’s
wavelength.
Rayleigh scattering
diffusion by larger particles which is not as
wavelength-dependent as Rayleigh scattering
Mie scattering
Light that is scattered at the same wavelength
as the incoming light is called
Rayleigh
scattering
Light that is scattered in transparent solids
due to vibrations (phonons) is called
Brillouin scattering
Light that is scattered due to vibrations in
molecules or optical phonons in solids is called
Raman scattering
Atoms or molecules that are excited to high
energy levels can decay to lower levels by
emitting radiation
emission or luminescence
For atoms excited by a high-temperature
energy source this light emission is commonly
called
atomic or optical emission.
atoms excited with light is called
atomic fluorescence
if the transition is between states of the
same spin it is called
fluorescence
if the
transition occurs between states of
different spin it is called
phosphorescence
allows EM
radiation to bend, pass through small apertures,
and move around small particles of matter.
diffraction
