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.
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 or ) 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