Chapter 2 Multiple Choice Questions

. A silyl radical bearing an Si-H· fragment has a g value of 2.0033 and a pair of lines separated by 15.5 MHz. Express the splitting in units of mT, Gauss and cm^-1.

15.5 MHz = 11.104 mT = 27.201 Gauss = 0.862 x 10^-4 cm^-1

15.5 MHz = 7.352 mT = 10.104 Gauss = 18.39 x 10^-4 cm^-1

15.5 MHz = 1.55 mT = 0.562 Gauss = 31.0 x 10^-4 cm^-1

15.5 MHz = 0.553 mT = 5.530 Gauss = 5.17 x 10^-4 cm^-1

15.5 MHz = 0.238 mT = 4.410 Gauss = 4.17 x 10^-4 cm^-1

. A Cu(II) metal ion (g_iso = 2.12) produces four lines with a separation of 500 MHz between each line. Express the hyperfine splitting in field units of mT and the hyperfine coupling in units of wavenumbers.

500 MHz = 0.185 mT = 0.29842 cm^-1

500 MHz = 16.850 mT = 0.01667 cm^-1

500 MHz = 32.953 mT = 0.76298 cm^-1

500 MHz = 45.672 mT = 2.86329 cm^-1

500 MHz = 52.984 mT = 3.4182 cm^-1

. A PO₃^- radical produces a pair of lines separated by 280 MHz with g_iso = 2.005. Calculate the expected resonant field positions of both lines in the X-band EPR spectrum (ν = 9.5 GHz).

B_res for m_I = -½ = 325.0 mT; B_res for m_I = +½ = 335.0 mT

B_res for m_I = -½ = 123.5 mT; B_res for m_I = +½ = 124.5 mT.

B_res for m_I = -½ = 333.5 mT; B_res for m_I = +½ = 343.5 mT.

B_res for m_I = -½ = 0.6785 mT; B_res for m_I = +½ = 0.679 mT.

B_res for m_I = -½ = 0.218 mT; B_res for m_I = +½ = 0.418 mT.

. The X-band (9.5 GHz) EPR spectrum of a matrix isolated Na atom reveals four hyperfine lines with resonant field positions of 3074 G, 3174 G, 3274 G and 3374 G. Calculate the g value of the atom.

g = 2.002

g = 1.950

g = 2.250

g = 2.005

g = 2.105

. Calculate the magnetic moment (μ_I) of a ¹³C nucleus.

6.1445 x 10^-27 J T^-1

3.1445 x 10^-27 J T^-1

9.1445 x 10^-27 J T^-1

1.1445 x 10^-28 J T^-1

0.0845 x 10^-28 J T^-1

. Calculate the polarization of a proton in a magnetic field of 335 mT and 10.5 T at 298 K.

6.345 x 10^-4 at 0.335 T; 9.871 x 10^-5 at 10.5 T

0.793 x 10^-4 at 0.335 T; 6.931 x 10^-7 at 10.5 T

1.148 x 10^-6 at 0.335 T; 3.598 x 10^-5 at 10.5 T

2.829 x 10^-2 at 0.335 T; 8.314 x 10^-4 at 10.5 T

4.126 x 10^-3 at 0.335 T; 2.142 x 10^-6 at 10.5 T

. The number of allowed energy levels for the ⁵⁵Mn nuclide are:

3

5

8

4

6

. The magnetic moment (μ_I) of an unknown nuclide is 2.884 x 10^-27 J T^-1. Given the nuclear spin is known to be 1, identify the unknown nuclide.

¹⁴N

²H

¹⁹F

⁶Li

³¹P

. Which one of the following statements is true:

Protons and neutrons have orbital and spin angular momentum.

Protons have orbital and spin angular momentum, neutrons have spin angular momentum.

Protons and neutrons possess orbital angular momentum only.

Protons and neutrons possess spin angular momentum only.

. Calculate the magnetic field responsible for the polarization of 2.5 x 10^-6 for ¹³C at 298 K.

0.5 T

1.2 T

2.9 T

100 T

250 T

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