Solid State Chemistry Questions and Answers – Intensities


This set of Solid State Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Intensities”.

1. Intensities of X-ray reflections is important because___________
a) The quantitative measurements of intensity are neccasary
b) X-ray is detected using intensity
c) Intensity is required during determining the concentration
d) The environmental condition is suited using intensities
View Answer

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
View Answer

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
View Answer

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
View Answer

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
View Answer

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
View Answer

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
View Answer

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
View Answer

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
View Answer

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
View Answer

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.

Sanfoundry Global Education & Learning Series – Solid State Chemistry.

To practice all areas of Solid State Chemistry, here is complete set of 1000+ Multiple Choice Questions and Answers.



Source link

Solid State Chemistry Questions and Answers – Modern X-Ray Powder Techniques and their Applications


This set of Solid State Chemistry Multiple Choice Questions & Answers (MCQs) focuses 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.
View Answer

Answer: d
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
View Answer

Answer: c
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
View Answer

Answer: b
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?
a) Temperature
b) Solubility
c) Concentration
d) Angle 2Θ
View Answer

Answer: d
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
View Answer

Answer: c
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
View Answer

Answer: d
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?
a) Temperature
b) Reflection
c) Resolution
d) Concentration
View Answer

Answer: c
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?
a) X-ray
b) Crystal monochromator
c) Gamma rays detector
d) Electron stopper
View Answer

Answer: b
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
View Answer

Answer: d
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
View Answer

Answer: b
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.

Sanfoundry Global Education & Learning Series – Solid State Chemistry.

To practice all areas of Solid State Chemistry, here is complete set of 1000+ Multiple Choice Questions and Answers.



Source link

Solid State Chemistry Questions and Answers – Effect of Stress on a Powder Pattern


This set of Solid State Chemistry Multiple Choice Questions & Answers (MCQs) focuses 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
View Answer

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
View Answer

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
View Answer

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
View Answer

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
View Answer

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
View Answer

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
View Answer

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
View Answer

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
View Answer

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
View Answer

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.

Sanfoundry Global Education & Learning Series – Solid State Chemistry.

To practice all areas of Solid State Chemistry, here is complete set of 1000+ Multiple Choice Questions and Answers.



Source link

Solid State Chemistry Questions and Answers – Sources of Background Radiation Fluorescence


This set of Solid State Chemistry test focuses on “Sources of Background Radiation Fluorescence”.

1. The collision between air molecules and diffracted X-ray are the___________
a) Sources of background scattering
b) Sources of front reflection
c) Sources of diffraction
d) Sources of background irradiation
View Answer

Answer: a
Explanation: The quality of an X-ray powder diffraction pattern is governed to a considerable extent by the level of background radiation which is present. Collisions between air molecules and diffracted X-ray beams are the sources of background scattering. For high quality Guinier focusing films it is worth while to evacuate the box containing the sample and film.

2. The fluorescent radiation is absorbed by placing a filter when__________
a) It is weak
b) It is strong
c) It is too much in quantity
d) It holds more energy
View Answer

Answer: a
Explanation: Fluorescent occurs when the sample acts as a secondary source of X-rays. If the fluorescent radiation is weak it may be absorbed by placing a filter between the sample and detector, e.g. a strip of nickel foil placed over the film.

3. If the fluorescent radiation is strong then which of the following parameters to be used?
a) Changing the path length of the secondary beam
b) Changing the wavelength of the primary beam
c) Keeping the wavelength of the secondary beam constant
d) Changing the frequency of the secondary beam
View Answer

Answer: b
Explanation: When the fluorescent radiation is strong then the wavelength of the primary beam is changed generally by replacing an X-ray tube containing a copper target by one with an iron or molybdenum target.

4. Fluorescent occurs when the radiation in the primary beam knocks out___________
a) Outer shell electrons
b) Inner shell electrons
c) Outer shell photon
d) Inner shell photon
View Answer

Answer: b
Explanation: Fluorescent occurs when the radiation in the primary beam that is emitted by the copper target knocks out inner shell electrons within atoms of the sample. Electrons in the outer shells drop down to occupy empty levels in the inner shells and in so doing they emit their excess energy in the form of X-rays.

5. Fluorescent radiation produced by electrons depends on which of the following factors?
a) Concentration of the photon
b) Solubility of the sample
c) Atomic number of the atoms
d) Frequency of the radiation
View Answer

Answer: c
Explanation: The inner shell electrons are knocked out and thus fluorescent radiation is produced, in this method fluorescent radiation depends on the atomic number of the atoms in the sample relative to that of the target material.

6. Cu Kα radiation of wavelength 1.5418 A˚, is generated by which of the following transition?
a) 1s→2p
b) 3s→1s
c) 2s→4s
d) 2p→1s
View Answer

Answer: d
Explanation: 2p→1s electronic transition generates the Cu Kα radiation of wavelength 1.5418 A˚ and in order to create a vacant 1slevel in the first place, 1s→∞ ionization potential is needed and this energy difference corresponds to a wavelength for copper of1.3804 A˚.

7. Cu Kα radiation can ionize 1s electrons in which of the following elements?
a) Cobalt
b) Helium
c) Nickel
d) Hydrogen
View Answer

Answer: a
Cu Kα radiation can ionize 1s electrons in cobalt and iron but not in nickel, helium and hydrogen. Because the ionization potentials of 1s electrons in nickel, cobalt and iron correspond to 1.4880, 1.6081 and 1.7433 A˚ and Cu Kα X-rays can ionize electrons in atoms whose ionization energy has a value corresponding to λ > 1.5418 A˚.

8. Lighter atoms _________
a) Fluoresce strongly
b) Fluoresce less strongly
c) Doesn’t Fluoresce
d) Fluoresce very very strongly
View Answer

Answer: b
Explanation: Lighter atoms also fluoresce, but less strongly, since fluorescence is strongest when the incident radiation has a wavelength that is only slightly shorter than the absorption edge (=IP) of the atoms.

9. When the X-rays strike a sample then the X-rays of the same wavelength as the incident beam is re-emitted and this is known as____________
a) Modified radiation
b) Same radiation
c) Coherent radiation
d) Non coherent radiation
View Answer

Answer: c
Explanation: When X-rays strike a sample two types of scattered rays are produced. In the first, the incident beam sets the electrons of the atoms into vibration, the X-rays of the same wavelength as the incident beam is re-emitted and are the characteristic diffracted radiation with which we are familiar. This is known as coherent, unmodified radiation.

10. Organic and organic based materials give which type of powder patterns?
a) Very good quality powder pattern
b) Very poor quality powder pattern
c) Doesn’t give powder pattern at all
d) High concentrated powder pattern
View Answer

Answer: b
Explanation: Due to the combined effects of reduced diffracted intensity and increased background intensity, organic and organic-based (e.g. polymeric) materials give poor quality powdered patterns.

Sanfoundry Global Education & Learning Series – Solid State Chemistry.

To practice all areas of Solid State Chemistry for tests, here is complete set of 1000+ Multiple Choice Questions and Answers.



Source link

Organic Chemistry Questions and Answers – Step Reaction Polymerisation


This set of Organic Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Step Reaction Polymerisation”.

1. Which of the following is true about Step-growth polymerisation?
a) radical, coordination, anionic, or cationic polymerization, depending on the type of initiation
b) polymerization that is catalysed by transition metal salts and complexes
c) monomers react by eliminating small molecules like H2O, NH3, CH2O and NaCl in a repetitive manner, Indefinite growth of the polymer occurs at both ends
d) monomers react to form first dimers, then trimmers, longer oligomers and eventually long chain polymers
View Answer

Answer: d
Explanation: Step-growth polymerization refers to a type of polymerization mechanism in which bi-functional or multifunctional monomers react to form first dimers, then trimmers, longer oligomers and eventually long chain polymer.

2. Which of the following is not true about step growth polymerisation?
a) Molar mass of backbone chain increases rapidly at early stage and remains approximately the same throughout the polymerization
b) Similar steps repeated throughout reaction process
c) Initiator are required for the step growth polymerisation
d) Rapid loss of monomer early in the reaction
View Answer

Answer: c
Explanation: Initiator is not required for the step growth polymerisation. Step-Growth polymerization occurs by consecutive reactions in which the degree of polymerization and average molecular weight of the polymer increase as the reaction proceeds.

3. Which of the following is polymer formed by step-growth polymerization is not classified under condensation polymerisation?
a) Polyester
b) Polyurethane
c) Polysiloxane
d) Polyamide
View Answer

Answer: b
Explanation: Most step-growth polymers are classified as condensation polymers, but not all step-growth polymers. Polyurethanes formed from isocyanate and alcohol bifunctional monomers) release condensates; in this case, we talk about addition polymers.

4. Which monomers are required for the formation of Bakelite via a typical step-growth polymerization?
a) phenol and formaldehyde
b) isocyanate and alcohol
c) diamine and formaldehyde
d) ester and phenol
View Answer

Answer: a
Explanation: The synthesis of first truly synthetic polymeric material, Bakelite, was announced by Leo Baekeland in 1907, through a typical step-growth polymerization fashion of phenol and formaldehyde.

5. Formation of polytriazole polymers via step-growth polymerization is produced from which of the following monomers?
a) Compound which bears both alkyne and azide functional group
b) Compound which bears both alkene and azide functional group
c) Compound which bears both alkane and azide functional group
d) Compound which bears both vinyl and azide functional group
View Answer

Answer: a
Explanation: Poly-Triazole polymers are produced from monomers which bear both an alkyne and azide functional group. The monomer units are linked to each other by the a 1,2,3-triazole group; which is produced by the 1,3-Dipolar cycloaddition, also called the Azide-alkyne Huisgen cycloaddition.

6. How does the reaction rate vary with increasing extent of reaction beyond 94% conversion in self catalyzed reaction?
a) decreases
b) increases
c) remains same
d) first increases than decreases
View Answer

Answer: a
Explanation: The kinetics of the step-growth polymerization can be described with Flory’s equal reactivity principle. If the polymerization is carried out in the presence of a strong acid (sulfonic acids) and if the catalyst concentration is kept constant throughout the process the average degree of polymerization increases linearly with the reaction time, which is a much more favorable situation for obtaining high average molecular weight polymers than the weak-acid catalyzed third-order reaction.

7. What is the trend in the molecular weight of step growth polymer at lower conversion and higher conversion respectively?
a) Increase then decrease
b) Decreases an increases
c) Remains same
d) Can’t say about molecular weight
View Answer

Answer: b
Explanation: Step-growth polymers increase in molecular weight at a very slow rate at lower conversions and reach moderately high molecular weights only at very high conversion (i.e., >95%).

8. Which of the following is not prepared by Ziegler-Natta coordination polymerisation?
a) High density Polyethylene (HDPE)
b) Ultrahigh molecular weight Polyethylene (UHMWPE)
c) Ethylene-1-alkenebcopolymer (linear low density polyethylene, LLDPE)
d) Polyvinyl acetate (PVAc)
View Answer

Answer: d
Explanation: Vinyl chloride is polar olefins and such alkenes do not polymerize in the presence of Ziegler-Natta or Kaminsky catalysts.

Sanfoundry Global Education & Learning Series – Organic Chemistry.

To practice all areas of Organic Chemistry, here is complete set of 1000+ Multiple Choice Questions and Answers.



Source link