ACHEM test questions and answer

ACHEM test questions and answers



_____ chemical analysis is the measurement of how much of a chemical substance is
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present. ______ chemical analysis is the determination of what is present in a sample. -
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answer-1. quantitative
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2. qualitative
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errors can be avoided by proper calibration and good experimental design - answer-
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systematic

_____ is used to compare standard deviations - answer-F-test
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_____ can be used to access the accuracy of an experiment - answer-standard
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reference material
v v




_____ is different from the analyte and helps account for differences in injection volume
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or sample loss - answer-internal standard
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Which statement about molecular spectroscopy is true
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a. phosphorescence is a non-radiative emission of light from a different spin state, T1 -->
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S0
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b. Beer's law fails when monochromatic light is used
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c. luminescent techniques are more sensitive than absorbance
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d. fluorescence spectroscopy is a molecular absorbance technique - answer-c.
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luminescent techniques are more sensitive than absorbance
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Which of the following statements are true of atomic emission spectroscopy (AES)?
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I. atoms are promoted to an excited state with a laser
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II. atoms are promoted to an excited state by gaining energy from collisions with other
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vatoms or from the high thermal energy of the flame
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III. the intensity of emitted light is proportional to analyte concentration
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IV. plasma often replaces flame in AES - answer-II. atoms are promoted to an excited
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vstate by gaining energy from collisions with other atoms or from the high thermal energy
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vof the flame
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III. the intensity of emitted light is proportional to analyte concentration
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IV. plasma often replaces flame in AES
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An electrode with a fixed potential is the:
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, a. cathode
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b. anode
v


c. indicator electrode
v v


d. reference electrode
v v


e. working electrode - answer-d. reference electrode
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The _______ gives the relative response of an ion-selective electrode to different
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species with the same charge
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a. counter ion coefficient
v v v


b. isoionic coefficient
v v


c. ion coefficient
v v


d. selectivity coefficient
v v


e. transient coefficient - answer-d. selectivity coefficient
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What is the purpose of the flame in atomic emission spectrometer? - answer-to atomize
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and excite the atoms to a higher atomic orbital
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True or False: fluorescence excitation spectra closely resemble absorbance spectra -
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answer-true
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True or False: emission spectra are higher energy than excitation energy - answer-false
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Which form of chromatography is NOT correctly defined?
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a. Adsorption chromatography - solute is adsorbed into solid particles
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b. partition chromatography - solute equilibrates between the stationary phase and
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mobile phase
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c. ion-exchange chromatography - solute ions of the opposite charge are attracted to the
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stationary phase
v v


d. size exclusion chromatography - solute is separated based on size
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e. affinity chromatography - solute binds to a molecule for a specific solute - answer-a.
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Adsorption chromatography - solute is adsorbed into solid particles
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solute equilibrates between the stationary phase and mobile phase - answer-partition
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chromatography
v




solute ions of the opposite charge are attracted to the stationary phase - answer-ion-
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exchange chromatography v




solute is separated based on size - answer-size exclusion chromatography
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solute binds to a molecule for a specific solute - answer-affinity chromatography
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A ____ is a plot of detector response vs. retention time
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