Discussion
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- Question
For a molecule to absorb IR, why must the molecule's vibrations cause fluctuations in the dipole moment of the molecule?
Options- A. Because a change in dipole moment lowers the energy required for electronic transitions
- B. Because for absorption to occur, the radiation must interact with the electric field caused by changing dipole moment
- C. Because fluctuations in the dipole moment allow the molecule to deform by bending and stretching
- D. All of the above
- Correct Answer
- Because for absorption to occur, the radiation must interact with the electric field caused by changing dipole moment
- 1. In the intersystem crossing
Options- A. the spin of an excited electron reverses, changing the state of the molecule (from singlet state to triplet state or vice versa)
- B. a molecule converts its excess energy to light, and emits a photon
- C. a molecule converts excess electronic energy to vibrational energy
- D. all of the above Discuss
- 2. Why phosphorescence measurements are usually made at a low temperature?
Options- A. To prevent thermal degradation of the phosphorescent species
- B. To promote phosphorescence by slowing the rate of radiationless transfer processes
- C. To increase the efficiency of the detector
- D. To decease the efficiency of detector Discuss
- 3. Why must the radiation source for fluorescence spectrometry be more powerful than for absorption spectroscopy?
Options- A. Because the magnitude of the output signal is proportional to the power of the incident radiation
- B. Because the sample won't fluoresce if the incident radiation is of low power
- C. To allow for scattering by the sample
- D. None of the above Discuss
- 4. What is the relationship between wavelength and wave number?
Options- A. Wavenumber = 1 / wavelength in centimeters
- B. Wavenumber - wavelength in nanometers = 1
- C. Wavelength in nanometers x wavenumber = 1
- D. None of the above Discuss
- 5. Where does a carbonyl (C=0) stretch appear in an IR spectrum?
Options- A. 1740-1720
- B. 1870-1650
- C. 3640-3250
- D. 160-110 Discuss
- 6. Why do fluorescence spectrometers often use double-beam optics?
Options- A. So a reference solution can be used
- B. To compensate for beam attenuation by the monochromator
- C. To compensate for power fluctuations in the radiation source
- D. All of the above Discuss
- 7. Fluorescence occurs when
Options- A. a molecule returns to the electronic ground state from an excited triplet state by losing it's excess energy as a photon
- B. a molecule returns to the electronic ground state from an excited singlet state by losing it's excess energy as a photon
- C. a molecule lowers its vibrational energy by losing it's excess energy as a photon
- D. none of the above Discuss
- 8. Internal conversion is where
Options- A. the spin of an excited electron reverses, changing the state of the molecule (from singlet state to triplet state or vice versa)
- B. A molecule converts its excess energy to light, and emits a photon
- C. A molecule converts excess electronic energy to vibrational energy
- D. none of the above Discuss
- 9. In gas chromatography, the basis for separation of the components of the volatile material is the difference in
Options- A. partition coefficients
- B. conductivity
- C. molecular weight
- D. molarity Discuss
- 10. Ion exchange chromatography is based on the
Options- A. electrostatic attraction
- B. electrical mobility of ionic species
- C. adsorption chromatography
- D. partition chromatography Discuss
UV Luminance Spectroscopy problems
Search Results
Correct Answer: the spin of an excited electron reverses, changing the state of the molecule (from singlet state to triplet state or vice versa)
Correct Answer: To promote phosphorescence by slowing the rate of radiationless transfer processes
Correct Answer: Because the magnitude of the output signal is proportional to the power of the incident radiation
Correct Answer: Wavenumber = 1 / wavelength in centimeters
Correct Answer: 1870-1650
Correct Answer: To compensate for power fluctuations in the radiation source
Correct Answer: a molecule returns to the electronic ground state from an excited singlet state by losing it's excess energy as a photon
Correct Answer: A molecule converts excess electronic energy to vibrational energy
Correct Answer: partition coefficients
Correct Answer: electrostatic attraction
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