Questions and answers for exam Preparation

MCQs

Total Questions : 147 | Page 13 of 15 pages

Question 121. What is the relationship between wavelength and wave number?

None of these
Wavenumber = 1 / wavelength in centimeters
Wavelength in nanometers x wavenumber = 1
Wavenumber - wavelength in nanometers = 1

Discuss Question

Answer: Option B. -> Wavenumber = 1 / wavelength in centimeters

Question 122. Internal conversion is where

A molecule converts excess electronic energy to vibrational energy
the spin of an excited electron reverses, changing the state of the molecule (from singlet state to triplet state or vice versa)
A molecule converts its excess energy to light, and emits a photon
None of these

Discuss Question

Answer: Option A. -> A molecule converts excess electronic energy to vibrational energy

Question 123. Fluorescence occurs when

a molecule returns to the electronic ground state from an excited singlet state by losing it's excess energy as a photon
a molecule returns to the electronic ground state from an excited triplet state by losing it's excess energy as a photon
None of these
a molecule lowers its vibrational energy by losing it's excess energy as a photon

Discuss Question

Answer: Option A. -> a molecule returns to the electronic ground state from an excited singlet state by losing it's excess energy as a photon

Question 124. Why phosphorescence measurements are usually made at a low temperature?

To promote phosphorescence by slowing the rate of radiationless transfer processes
To prevent thermal degradation of the phosphorescent species
To increase the efficiency of the detector
To decease the efficiency of detector

Discuss Question

Answer: Option A. -> To promote phosphorescence by slowing the rate of radiationless transfer processes

Question 125. The sequence of amino acids in proteins can be determined by means of

partial cleavage of the original polypeptide into smaller polypeptides
identification of the -COOH terminal amino acids
identification of the -NH2 terminal amino acids
All of these

Discuss Question

Answer: Option D. -> All of these

Question 126. What is meant by rotating frame of reference?

None of these
That the sample is spun rapidly in the applied field
That the detector rotates around the sample
If the laboratory itself is imagined to be rotated at the Larmor frequency, viewing that individual magnetic moment vectors are fixed in space

Discuss Question

Answer: Option D. -> If the laboratory itself is imagined to be rotated at the Larmor frequency, viewing that individual magnetic moment vectors are fixed in space

Question 127. Why is it advantageous to record many FID signals from the same sample and then add them together?

To remove inaccuracies caused by fluctuations in the applied magnetic field
To ensure that all target nuclei in the sample have been excited
To increase sensitivity
None of these

Discuss Question

Answer: Option C. -> To increase sensitivity

Question 128. Which of the following is the basis of first dimension of separation for two-dimensional electrophoresis?

Solubility
Isoelectric point
Folding
Molecular mass

Discuss Question

Answer: Option B. -> Isoelectric point

Question 129. In FT-NMR, how are nuclei excited?

By an intense pulse of radiation which contains a wide range of frequencies
None of these
By an intense pressure
By radio-frequency radiation whose frequency is swept across a predetermined range

Discuss Question

Answer: Option D. -> By radio-frequency radiation whose frequency is swept across a predetermined range

Question 130. What is the name given to the relaxation process due to an interaction between an excited nucleus and the magnetic fields caused by nuclei in molecules moving around in the sample?