Magnetism Exercises

These questions deal in part with concepts presented in today's lecture and assigned online readings.
  1. Use equation 5 from the paper by Bain and Berry to estimate the diamagnetic susceptibility χD of AsPh3. How does this value compare to that calculated using Pascal's constants?
  2. In a high molecular weight metalloenzyme containing a single paramagnetic metal center, an accurate diamagnetic correction is required in order to derive the value of the paramagnetic susceptibility. What is the approach taken in such a circumstance?
  3. What is the value of χPT that is expected for [Cr(OH2)6]3+ based upon equation 3a of the paper by Bain and Berry?
  4. Why must we subtract the value of the diamagnetic susceptibility χD from the measured susceptibility χM in order to determine the paramagnetic susceptibility, χP?
  5. A 0.012 M solution of (OCN)Mo(N[tBu]Ar)3, where Ar = 3,5-C6H3Me2, gave rise to a frequency shift (Δν from Evans's method) of 37.17 Hz using a modern 300 MHz spectrometer at 298 K. What are the values of χPT and μeff? Note: here is an online molecular weight calculator.
  6. For the preceding example, how many unpaired electrons are indicated?
  7. A compound having the formula [Co(NO2)2(en)2] shows a frequency shift Δν of 35 Hz at 298 K at a concentration of 0.025 M. Is this a high-spin complex? Note: you can make use of our interactive online spreadsheet for Evans's method calculations.
  8. What is different about the configuration of modern high-field NMR spectrometers (compared with the early permanent magnet NMR spectrometers) that necessitated revision of the Evans's method equations?

The above exercises are intended to help you prepare for our final exam. They do not need to be handed in and will not be graded.

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