This set of Solid State Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Effect of Stress on a Powder Pattern”.
MCQs based on Effect of Stress on a Powder Pattern:
1. Crystals experience anomalous powder patterns under___________
a) Strain
b) Change in temperature
c) Change in concentration
d) Stress
Answer: d
Explanation: Crystals exhibit anomalous powder patterns when they are under stress. Two types of stress can be applied one uniform compressive stress another non-uniform stress. Stress is force acted upon on a crystal per unit area of the crystal.
2. Contraction of the unit cell in the crystal occurs during which of the following phenomenon?
a) Uniform strain is applied
b) Uniform stress is applied
c) Non uniform stress is applied
d) Non uniform strain is applied
Answer: b
Explanation: The whole powder pattern of the crystal may be shifted to lower d-spacings if the crystals are under a uniform compressive stress such that a contraction of unit cell occurs inside the crystal.
3. The powdered line are broadened in the crystal during which of the following phenomenon?
a) Uniform strain is applied
b) Uniform stress is applied
c) Non uniform stress is applied
d) Non uniform strain is applied
Answer: c
Explanation: When a non uniform stress is applied to the crystal, different crystals or different parts of the same crystal may be deformed to differing degrees and the powder lines become broadened.
4. Stress is caused on the crystal by which of the following factor?
a) External strain applied
b) Internal stress
c) External pressure
d) External change in temperature
Answer: c
Explanation: Stresses on the crystal is caused by the application of an external pressure for example the working hard of the metals in which residual distortions are present in the crystal after treatment.
5. Chemical reaction inside the crystal can cause________
a) Change in external temperature
b) Change in concentration
c) Stress
d) Change in solubility
Answer: c
Explanation: Stress in the crystal can be generated internally as a consequence of a chemical reaction taking place inside the crystals, for example coherent precipitation of supersaturated solid solutions, age hardening of metals and ceramics etc.
6. Stress is caused or generated internally by the consequence of chemical reaction taking place in the crystal, one of its example is occurrence of phase transitions during __________
a) Change in concentration
b) Change in solubility
c) Change in force
d) Change in temperature
Answer: d
Explanation: Phase transition occurs I the crystals during cooling (if there is a change in the volume or shape of the crystals and they are embedded in a solid matrix, then the rigid environment of the matrix may prevent the transition from occurring to completion).
7. Unit cell parameters are determined by which of the following parameters?
a) Double crystal X-ray photographs
b) Single crystal X-ray photographs
c) Double crystal Gamma rays graphs
d) Single crystal Gamma rays graphs
Answer: b
Explanation: The unit cell parameters in the crystal are often determined with the aid of single crystal X-ray photographs. The symmetry or unit cell type is first obtained from an inspection of the photographs.
8. What are the limitations for the accuracy of the values for the unit cell parameters?
a) Lack of sufficient temperature
b) Insufficient amount of the unit cells
c) Shrinkage of film
d) Lack of external pressure
Answer: c
Explanation: There are several intrinsic limitations to the accuracy of the values thus obtained-lack of the internal standard, shrinkage of film, etc. And the accuracy of axial parameters is usually to between 0.05 and 0.2 percent.
9. Accurate cell parameters can be obtained from a least squares refinement of the _______________
a) S-spacings
b) Vacant p shells
c) d-spacings
d) vacant f shells
Answer: c
Explanation: Accurate cell parameters may be obtained from a least squares refinement on the d-spacings of at least several high angle powder lines whose indexing is known for certain.
10. The intensities of various candidate reflections estimated qualitatively from the indexed single crystal photographs and the strongest of these almost certainly correspond to the reflection that gives___________
a) powder line
b) curve
c) stress
d) strain
Answer: a
Explanation: The strongest of the various candidate reflections corresponds to the reflection that gives the powder line that is because spots that are weak on single crystal photographs are not usually observed in powder photographs unless the latter are grossly overexposed.
Source link