Worksheet: Comparing Spectroscopic Methods

In this worksheet, we will practice comparing the applications of spectroscopic methods and the processes responsible for the production of signals.

Q1:

Which of the following is affected by infrared radiation?

  • AValence electrons
  • BNuclear spin
  • CMolecular vibrations
  • DCore electrons
  • EMolecular rotations

Q2:

Which of the following is affected by ultraviolet and visible radiation?

  • AMolecular vibrations
  • BCore electrons
  • CValence electrons
  • DNuclear spin
  • EMolecular rotations

Q3:

What does proton NMR tell you, primarily, about a molecule?

  • AWhether there are any hydrogens present in the molecule and what their chemical shift is with respect to a standard (TMS)
  • BThe kind of heteroatoms near the hydrogens you observe in the spectrometer
  • CThe kind of hydrogens present (what each kind is bonded to) and exactly how many there are relative to each other
  • DWhether electron-donating or electron-withdrawing groups are present in the molecule

Q4:

Which of the following is an accurate definition of mass spectrometry?

  • ACareful weighing of molecules using supersensitive nanobalances constructed with microlithography
  • BThe breakdown and ionization of molecules with high-energy electrons, followed by magnetic separation of the charged fragments and analysis of their mass-to-charge ratios
  • CAnalysis of the charges of molecular ions produced by fragmentation of molecules in a magnetic field
  • DAnalysis of the masses of whole molecules that have been given an electric charge using a voltameter

Q5:

What does the combination of broad peaks and sharper ones that UV spectroscopy generally shows tell us?

  • AHow many heteroatoms are in the molecule
  • BThe degree of conjugation (𝜋 electron delocalization) and something about substitution patterns
  • CWhat atoms are attached to a double bond or aromatic ring
  • DWhat the elemental composition of the molecule is

Q6:

How is infrared spectroscopy different from UV-vis and NMR spectroscopies?

  • AInfrared spectroscopy overlaps with UV-vis spectroscopy in the electromagnetic spectrum, providing complimentary information on functional groups, while NMR looks at electronic configuration and bonding.
  • BInfrared spectroscopy detects vibrational motions of functional groups whereas UV-vis spectroscopy sees electronic transitions and NMR spectroscopy looks at the nuclear magnetic moment transition energy.
  • CThey all see different parts of the molecule, and, specifically, different atoms and how they’re joined together.
  • DIt uses a different energy range from UV-vis spectroscopy but the same range as NMR spectroscopy.

Q7:

Which of the following best describes the relative interaction energies used in various kinds of spectroscopic methods?

  • ANMR < IR < UV-Vis ≤ mass spectrometry
  • BThe energy used does not matter since this can vary independently of frequency or wavelength.
  • CNMR < UV-Vis < mass spectrometry < IR
  • DYou cannot compare the energies since each type of spectroscopy uses a unique mixture of frequencies.

Q8:

Which of the following is a general description of spectroscopic methods?

  • AThe excitation of molecules with heat or light so that they emit vibrational energy that can be detected with spectrometers
  • BThe use of visible or ultraviolet light to illuminate molecules so that they can be observed using a microscope
  • CThe use of electromagnetic waves to change the shape or structure of molecules so that they can be observed using a microscope
  • DThe measurement of chemical interactions with electromagnetic waves to obtain information about molecular structure and properties

Q9:

Infrared was one of the first spectroscopic methods and is still widely used today to characterize molecules because:

  • AIt is easy to do, takes very little sample and gives specific information about what functional groups are present in the molecule.
  • BIt tells you more about the molecule than any other technique.
  • CIt uses the least expensive analytical equipment available.
  • DYou can sample solids, liquids or gases although the information obtained is not useful without combining with other techniques of analysis.

Q10:

Which of the following is true for ultraviolet spectroscopy?

  • AWe can see the broad peaks in the spectrum given by ionized fragments, and this tells us what kinds of bonds are involved.
  • BIt is most sensitive to carbonyl bonds and less sensitive to aromatic and conjugated double bonds.
  • CAll types of bonding can be detected, from 𝜎 bonds to 𝜋 bonds, to conjugated and aromatic bonding.
  • DDouble bonds, aromatic rings, and conjugated unsaturation can be detected.

Q11:

Which of the following information about a molecule is determined mainly using infrared spectroscopy?

  • AThe exact kind and number of each functional group in the analyte.
  • BIts purity and what kinds of impurities are present in the mixture.
  • CThe total number of atoms and what kind of them is in the molecule.
  • DWhat kinds of functional groups like amides, ethers, and alkene double bonds are present in the molecule.

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