INSTRUMENTAL ANALYSIS EXAM
QUESTIONS AND DETAILED ANSWERS.
EXPERT VERIFIED FOR GUARANTEED
PASS.
What is a molecular ion? - ANS a radical ion, formed by loss of one e⁻ after collision with a
stream of other e⁻. The molecular ion has the same molecular mass as the molecule
What is fragmentation? - ANS Relaxation of newly formed excited state molecular ions by
breaking up to produce ions of lower masses.
What is rearrangement? - ANS process that occurs when a fragment still has a lot of energy
and must lose that energy in some way
What ions are attracted through the slit of a mass spectrometer? - ANS positive ions
What are daughter ions? - ANS the lower-mass ions formed by extensive fragmentation of
the molecular ion during its relaxation following its EI-induced formation
What is a base peak? - ANS The largest peak on a spectrum, which is arbitrarily assigned a
value of 100 This peak corresponds to the most abundant ion in the sample, presumably
formed by breaking the weakest bond in the structure
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, What is a peak's relative intensity? - ANS a measure of that peak's height (intensity) as a
percentage of the base-peak height
What are collision product peaks? - ANS ∙peaks at higher mass numbers than that of the
molecular ion, resulting from ion-molecule collisions
What peak is produced by the protonated molecular ion collision product (transfer of H atom to
the molecular ion)? - ANS ∙an enhanced (M+1)⁺ peak
What determines the height of the (M+1)⁺ collision product peak formed by protonation of the
molecular ion? - ANS This transfer is a second-order reaction, and the amount of product
depends strongly on the reactant concentration. Consequently, the height of this (M + 1)⁺ peak
increases much more rapidly with increases in sample pressure than do the heights of other
peaks, make it possible to detect this atom-transfer reaction
What is a hard ionization source? - ANS ionization sources that impart enough energy to
analyte molecules to leave them in a highly excited energy state. Relaxation then involves
rupture of bonds, producing fragment ions that have mass-to- charge ratios less than that of
the molecular ion.
What is a soft ionization source? - ANS ∙cause little fragmentation
∙usually produces the molecular ion and only a few, if any, other peaks
What are ionizing agents for MS? - ANS the mechanisms used to ionize the sample
What are gas-phase sources? - ANS With a gas-phase source, the sample is first vaporized
and then ionized
What are the ionizing agents for the gas-phase sources? - ANS
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QUESTIONS AND DETAILED ANSWERS.
EXPERT VERIFIED FOR GUARANTEED
PASS.
What is a molecular ion? - ANS a radical ion, formed by loss of one e⁻ after collision with a
stream of other e⁻. The molecular ion has the same molecular mass as the molecule
What is fragmentation? - ANS Relaxation of newly formed excited state molecular ions by
breaking up to produce ions of lower masses.
What is rearrangement? - ANS process that occurs when a fragment still has a lot of energy
and must lose that energy in some way
What ions are attracted through the slit of a mass spectrometer? - ANS positive ions
What are daughter ions? - ANS the lower-mass ions formed by extensive fragmentation of
the molecular ion during its relaxation following its EI-induced formation
What is a base peak? - ANS The largest peak on a spectrum, which is arbitrarily assigned a
value of 100 This peak corresponds to the most abundant ion in the sample, presumably
formed by breaking the weakest bond in the structure
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
, What is a peak's relative intensity? - ANS a measure of that peak's height (intensity) as a
percentage of the base-peak height
What are collision product peaks? - ANS ∙peaks at higher mass numbers than that of the
molecular ion, resulting from ion-molecule collisions
What peak is produced by the protonated molecular ion collision product (transfer of H atom to
the molecular ion)? - ANS ∙an enhanced (M+1)⁺ peak
What determines the height of the (M+1)⁺ collision product peak formed by protonation of the
molecular ion? - ANS This transfer is a second-order reaction, and the amount of product
depends strongly on the reactant concentration. Consequently, the height of this (M + 1)⁺ peak
increases much more rapidly with increases in sample pressure than do the heights of other
peaks, make it possible to detect this atom-transfer reaction
What is a hard ionization source? - ANS ionization sources that impart enough energy to
analyte molecules to leave them in a highly excited energy state. Relaxation then involves
rupture of bonds, producing fragment ions that have mass-to- charge ratios less than that of
the molecular ion.
What is a soft ionization source? - ANS ∙cause little fragmentation
∙usually produces the molecular ion and only a few, if any, other peaks
What are ionizing agents for MS? - ANS the mechanisms used to ionize the sample
What are gas-phase sources? - ANS With a gas-phase source, the sample is first vaporized
and then ionized
What are the ionizing agents for the gas-phase sources? - ANS
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