This set of Solid State Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Intensities”.
MCQ’s based on Intensities:
1. Intensities of X-ray reflections is important because___________
a) The quantitative measurements of intensity are necessary
b) X-ray is detected using intensity
c) Intensity is required during determining the concentration
d) The environmental condition is suited using intensities
Answer: a
Explanation: Intensities of X-rays are important for two main reasons. First, quantitative measurements of intensity are necessary in order to determine unknown crystal structures. Second, qualitative or semi-quantitative intensity data are needed in using the power fingerprint method to characterize materials and especially in using the powder diffraction file to identify unknowns.
2. Atoms diffract or scatter X-rays because of__________
a) Incident visible light
b) Incident X-ray beam
c) Incident gamma ray
d) Incident electrons
Answer: b
Explanation: An Atom diffract or scatter X-rays because of incident X-ray beam which can be described as an electromagnetic wave with an oscillating electric field, sets each electron of an atom into vibration.
3. The electrons of an atom act as which of the following options for the sources of X-rays?
a) Electrode
b) Primary source
c) Secondary source
d) Tertiary source
Answer: c
Explanation: A vibrating charge such as an electron emits radiation and this radiation in in phase or coherent with the incident X-ray beam. The electrons of an atom therefore act as the secondary point sources of X-rays.
4. The intensity of the radiation scattered coherently by ‘point source’ electrons has been treated theoretically and is given by which of the following equations?
a) Einstein equation
b) Maxwell equation
c) Stockbarger equation
d) Thomson equation
Answer: d
Explanation: Thomson equation is given by:-
Ip α ½( 1+ cos22Θ)
Here, Ip is the scattered intensity at any point P, and 2Θ is the angle between the directions of the incident beam and the diffracted beam that passes through P, from this equation it can be seen that the scattered beams are most intense when parallel or antiparallel to the incident beam and the weakest when at 90˚ to the incident beam.
5. Thomson equation is also known as _________
a) Diffraction factor
b) Reflection factor
c) Polarization factor
d) Thomson factor
Answer: c
Explanation: The Thomson equation which is used to measure the intensity of the radiation scattered coherently by ‘point source’ electrons is also known as polarization factor and is one of the standard angular correction factors that must be applied during the processing of intensity data (for use in structure (determination).
6. For the non-crystalline beams are scattered by the atoms _________
a) From top to bottom
b) In horizontal direction
c) In vertical direction
d) In all direction
Answer: d
Explanation: Each atom in a material acts as a secondary point source of X-rays. If the material is non-crystalline, beams are scattered by the atoms in all directions, but in crystalline materials the scattered beams interfere destructively in most possible directions.
7. Intensities depends on which of the following factors?
a) Solubility of the solid
b) Emission factor
c) Refraction factor
d) Absorption factor
Answer: d
Explanation: Intensities depend on several factors, one of its factor is absorption factor, absorption of X-rays by the sample and depend on the form of the sample and geometry of the instrument. Ideally, for single crystal work, crystals should be spherical so as to have the same absorption factor in all directions.
8. An electron density is a plot of variation of ______
a) Electron density
b) Electron solubility
c) Electron mass
d) Electron volume
Answer: a
Explanation: A plot of variation of electron density throughout the unit cell is known as electron density map. During the process of the solving an unknown structure it is often useful to construct electron density maps in order to try and locate atoms.
9. An electron map resembles which of the following options?
a) Electron spectrum
b) Geographical contour map
c) Diffraction spectrum
d) Resolution electron map
Answer: b
Explanation: An electron map resembles a geographical contour map. The contours represent lines of constant electron density throughout the structure. Peaks of the electron density maxima may be distinguished clearly and these correspond to the atoms, the coordinates of the atoms in the unit cell are given by the coordinates of the peak maxima.
10. The mental picture of atom is sphere can be given by which of the following?
a) Pauli exclusion principle
b) Maxwell equation
c) Electron density map
d) Stockbarger equation
Answer: c
Explanation: Electron density maps also show that our mental picture of atoms as spheres is essentially correct, at least on a time average. The electron density drops to almost zero at some point along point along the line connecting pairs of adjacent atom and this supports the model of ionic bonding in NaCl.