This set of Solid State Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Modern X-Ray Powder Techniques and their Applications”.
MCQ based on Modern X-Ray Powder Techniques and their Applications:
1. A powder diffractometer is an___________
a) Electron density instrument
b) Powder electron refraction instrument
c) X-ray spectrum detector instrument
d) Powder X-ray instrument.
Explanation: The most commonly used powder X-ray instrument is the powder diffractometer. It has a proportional, scintillation or Geiger counter as the detector which is connected to a chart recorder or sometimes to a means of digital output.
2. In the powder diffractometer, the counter is set, the counter is set to scan at a ________
a) Variable temperature
b) Constant temperature
c) Constant angular velocity
d) Variable angular velocity
Explanation: In normal use, the counter in the powder diffractometer is set to scam over a range of 2Θ values at a constant angular velocity, it is common practice to refer to the angle 2Θ between the diffracted and undiffracted beams, rather than to the Bragg angle, Θ.
3. The intensities in the powder diffractometer is taken as________
a) very low height
b) peak height
c) constant height
d) variable height
Explanation: In the powder diffractometer, the intensities are taken as peak height, unless very accurate work is being done, in which case areas may be measured, the most intense peak is given the intensity of 100 and the rest are scaled accordingly.
4. In the powder diffractometer, a correction factor varies with which of the following factors?
d) Angle 2Θ
Explanation: A correction factor in the powder diffractometer varies with 2Θ, is obtained from the discrepancy between observed and the true d-spacings of the standard and is then applied to the pattern that is being measured.
5. Which of the following phenomenon takes place when the arrangement of the crystal is not random?
a) The temperature increases
b) The temperature decreases
c) Preferred orientation exits
d) Preferred orientation enters
Explanation: If the crystal arrangement is not random, then preferred orientation exists and can introduce errors, sometimes very large, into the measured intensities preferred orientation is a serious problem for the materials that crystallize in a characteristic, very non-spherical shape like clay minerals, etc.
6. Which one of the following is the big disadvantage of the Debye-Scherrer cameras?
a) High intensity diffracted beams
b) High intensity refracted beams
c) Low intensity refracted beams
d) Divergent diffracted beams
Explanation: The big disadvantage of early Debye-Scherrer cameras is that incident and diffracted beams are inevitable, somewhat divergent and of low intensity. In diffractometer and the modern focusing cameras, a convergent X-ray beam is used.
7. Using the convergent X-ray in powder diffractometer which of the following factor is affected?
Explanation: In diffractometer and the modern focusing cameras, a convergent X-ray beam is used, this gives a dramatic improvement in resolution and because much more intense beams may be used, exposure time ate greatly reduced.
8. Which one of the following is an additional feature of the focusing cameras?
b) Crystal monochromator
c) Gamma rays detector
d) Electron stopper
Explanation: In the focusing cameras an additional feature is the crystal monochromator which serves two functions, to give highly monochromatic radiation and to produce an intense, convergent X-ray beam.
9. A crystal monochromator contains which of the following material?
a) X-ray beam detector
b) A very small crystal
c) Crystal electrode
d) Large single crystal
Explanation: A crystal monochromator consists of a large single crystal of for example quartz oriented such that one set of planes which diffracts strongly for quartz is at the Bragg angle to the incident beam.
10. For the accurate measurement of the d-spacings which of the following method is best to use?
a) Stockbarger method
b) Refractometry method
c) Diffractometry method
d) Dalton method
Explanation: In order to measure the d-spacings accurately, Diffractometry is normally regarded as the best method and most of the patterns in the powder diffraction file gave been obtained by the Diffractometry. An internal standard of accurately known d-spacings must be added to the sample in order to eliminate the instrumental error.