instrumental analysis ch. 20, 21, 22, 23, 24 questions
with verified answers
A chemist uses atomic absorption spectroscopy to measure the amount
of calcium in a urine sample. When preparing the sample for analysis,
the chemist adds an excess of La3+ to the sample. Why is La3+ added to
the urine sample? Ans✓✓✓ La3+ binds to PO3−4 in the urine sample
which prevents the formation of Ca3(PO4)2(s) and frees the Ca2+ in the
sample to be atomized.
A flame can be used in both atomic absorption and atomic emission
spectroscopy to atomize the sample. In which technique is a stable
flame temperature more critical? Why? Ans✓✓✓ A stable flame
temperature is more critical in atomic emission spectroscopy because a
small fluctuation in the temperature can greatly effect the excited-state
population of the atoms in the sample.
A gas chromatography column containing a
(cyanopropylphenyl)0.14(dimethyl)0.86polysiloxane stationary phase is
used to separate the molecules listed. Place the molecules in the order
they will elute from the column. Ans✓✓✓ heptane
benzene
butanol
octane
1-nitropropane
nonane
,A sample containing the analyte molecule JKLMNJKLMN is injected into
a tandem mass spectrometer from a chromatographic column
Ans✓✓✓ sample->ion source->mass analyzer1->collision cell-> mass
analyzer 2-> detector
A young researcher set out to develop a method for quantifying the
polycyclic aromatic hydrocarbon (PAH) content in a contaminated soil
sample by gas chromatography (GC). With an analysis goal already
chosen, in what order should the young researcher proceed to
complete the analysis? Ans✓✓✓ select a sample preparation method,
select a detector, select a column, and choose a sample injection
method
Absorption Chromatography Ans✓✓✓ Solute molecules equilibrate
between the mobile phase and the surface of the stationary phase
Adjusted retention time Ans✓✓✓ the time required by a retained
solute to travel through the column beyond the time required by the
unretained solvent
advantages of Zeeman background Ans✓✓✓ Accuracy, operates at the
analyte wavelength, speed at which the correlation is completed
affinity chromatography Ans✓✓✓ specific groups are attached to the
stationary phase to attract the solute
, Anode Ans✓✓✓ For every one photon that strikes the PMT,10^6
electrons are collected at its surface
Aromatic and unsaturated compounds Ans✓✓✓ thermal conductivity
mass spectrometer
photoionization
Arrange the fuel-oxidant pairs based on the temperature of the flame
they produce from highest to lowest. Ans✓✓✓ Cyanogen-oxygen,
acetylene-oxygen, acetylene-nitrous oxide, hydroen-oxygen, acetylene-
air, h2-air
atomic analysis methods in order of increasing sensitivity. Ans✓✓✓
Flame atomic absorption, furnace atomic absorption, plasma emission,
and inductive coupled plasma mass spectrometry
attenuated total reflectance sensor Ans✓✓✓
baffle Ans✓✓✓ It promotes further mixing of the mist, oxidation, and
fuel, and prevents large droplets from reaching the flame.
band broadening in gas-liquid chromatography. Ans✓✓✓ very high
flow rates
slow injection rate
with verified answers
A chemist uses atomic absorption spectroscopy to measure the amount
of calcium in a urine sample. When preparing the sample for analysis,
the chemist adds an excess of La3+ to the sample. Why is La3+ added to
the urine sample? Ans✓✓✓ La3+ binds to PO3−4 in the urine sample
which prevents the formation of Ca3(PO4)2(s) and frees the Ca2+ in the
sample to be atomized.
A flame can be used in both atomic absorption and atomic emission
spectroscopy to atomize the sample. In which technique is a stable
flame temperature more critical? Why? Ans✓✓✓ A stable flame
temperature is more critical in atomic emission spectroscopy because a
small fluctuation in the temperature can greatly effect the excited-state
population of the atoms in the sample.
A gas chromatography column containing a
(cyanopropylphenyl)0.14(dimethyl)0.86polysiloxane stationary phase is
used to separate the molecules listed. Place the molecules in the order
they will elute from the column. Ans✓✓✓ heptane
benzene
butanol
octane
1-nitropropane
nonane
,A sample containing the analyte molecule JKLMNJKLMN is injected into
a tandem mass spectrometer from a chromatographic column
Ans✓✓✓ sample->ion source->mass analyzer1->collision cell-> mass
analyzer 2-> detector
A young researcher set out to develop a method for quantifying the
polycyclic aromatic hydrocarbon (PAH) content in a contaminated soil
sample by gas chromatography (GC). With an analysis goal already
chosen, in what order should the young researcher proceed to
complete the analysis? Ans✓✓✓ select a sample preparation method,
select a detector, select a column, and choose a sample injection
method
Absorption Chromatography Ans✓✓✓ Solute molecules equilibrate
between the mobile phase and the surface of the stationary phase
Adjusted retention time Ans✓✓✓ the time required by a retained
solute to travel through the column beyond the time required by the
unretained solvent
advantages of Zeeman background Ans✓✓✓ Accuracy, operates at the
analyte wavelength, speed at which the correlation is completed
affinity chromatography Ans✓✓✓ specific groups are attached to the
stationary phase to attract the solute
, Anode Ans✓✓✓ For every one photon that strikes the PMT,10^6
electrons are collected at its surface
Aromatic and unsaturated compounds Ans✓✓✓ thermal conductivity
mass spectrometer
photoionization
Arrange the fuel-oxidant pairs based on the temperature of the flame
they produce from highest to lowest. Ans✓✓✓ Cyanogen-oxygen,
acetylene-oxygen, acetylene-nitrous oxide, hydroen-oxygen, acetylene-
air, h2-air
atomic analysis methods in order of increasing sensitivity. Ans✓✓✓
Flame atomic absorption, furnace atomic absorption, plasma emission,
and inductive coupled plasma mass spectrometry
attenuated total reflectance sensor Ans✓✓✓
baffle Ans✓✓✓ It promotes further mixing of the mist, oxidation, and
fuel, and prevents large droplets from reaching the flame.
band broadening in gas-liquid chromatography. Ans✓✓✓ very high
flow rates
slow injection rate
