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

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

Q2:

In a 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?

  • ACore electrons
  • BValence electrons
  • CMolecular vibrations
  • DNuclear spin
  • EMolecular rotations

Q4:

The electromagnetic radiation used for NMR spectroscopy falls in which region?

  • AX-ray
  • BMicrowave
  • CGamma ray
  • DRadio wave
  • EUltraviolet

Q5:

In which units are NMR chemical shifts usually reported?

  • A MHz
  • B Hz
  • C nm
  • D ppm

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 also change.
  • CThe chemical shift and resonance frequency remain constant.
  • DThe chemical shift remains constant; the resonance frequency changes.
  • EThere is no way to predict the effect.

Q7:

NMR involves what kind of analysis?

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

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