Worksheet: Generating NMR Spectra

In this worksheet, we will practice generating an applied magnetic field and using an RF pulse to produce NMR spectra from spin-active nuclei.

Q1:

In an NMR experiment, an external magnetic field is applied to the sample. What happens to the protons in the sample?

  • AAll protons assume a random orientation.
  • BAll protons align opposite to the field.
  • CAll protons align with the field.
  • DSome protons align with the field and some align opposite to it.

Q2:

In an NMR experiment, a radio frequency (RF) signal is applied to the sample, in addition to the magnetic field. What happens to the spins of the sample?

  • AThe RF will force all spins to assume a random orientation.
  • BThe RF will force all spins to align opposite to the magnetic field.
  • CThe RF will force all spins to align with the magnetic field.
  • DThe RF will flip the spin, inducing a spin transition to a slightly higher-energy state.

Q3:

Which of the following molecular properties is affected by the measurement of an NMR spectrum?

  • AMolecular vibrations
  • BMolecular rotations
  • CValence electrons
  • DCore electrons
  • ENuclear spin

Q4:

In which region does the electromagnetic radiation used for NMR spectroscopy fall?

  • AGamma ray
  • BRadio wave
  • CX-ray
  • DMicrowave
  • EUltraviolet

Q5:

In which units are NMR chemical shifts usually reported?

  • AHz
  • Bppm
  • Cppb
  • DMHz
  • Enm

Q6:

In NMR spectroscopy, what happens to the chemical shift and resonance frequency of a compound when the spectrometer frequency changes?

  • AThe chemical shift changes; the resonance frequency remains constant.
  • BThe chemical shift and resonance frequency remain constant.
  • CThe chemical shift and resonance frequency also change.
  • DThere is no way to predict the effect.
  • EThe chemical shift remains constant; the resonance frequency changes.

Q7:

What kind of analysis does NMR involve?

  • AUsing high energy beams to excite the electrons so they can be detected by magnetic field fluctuations
  • BMagnetizing the molecules so they can be separated by traveling through a vacuum down a long tube surrounded by static magnets
  • CSpinning nuclei in such a way that they can be seen with infrared radiation and functional groups determined from the frequency
  • DUsing radio waves to detect nuclei present in a molecule (such as H or C) and based on extensive data bases of chemical shifts to determine what each type is bonded to

Q8:

Fill in the blank: Nuclear magnetic resonance (NMR) spectroscopy makes use of liquid helium in order to generate large magnetic fields. The metals involved in creating these fields are behaving as .

  • Ahigh-temperature superconductors
  • Bintrinsic semiconductors
  • Cextrinsic semiconductors
  • Dlow-temperature superconductors

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