Crystalline solids MCQs With Answer

Crystalline solids MCQs With Answer provide B. Pharm students a focused way to master solid-state chemistry relevant to pharmaceutics. This introduction covers key concepts like unit cell, Bravais lattices, packing efficiency, Miller indices, X-ray diffraction (PXRD), polymorphism, hydrates/solvates, crystal defects, and their impact on drug stability, solubility, and dissolution. Emphasis on analytical techniques (DSC, Scherrer equation, Rietveld) and crystallization principles helps bridge theory with formulation challenges. These keyword-rich MCQs strengthen understanding of crystalline behavior, solid-state characterization, and formulation strategies essential for drug development. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What defines a crystalline solid?

• A material with atoms arranged in a regular, repeating three-dimensional pattern
• A solid with only amorphous regions and no long-range order
• A substance that melts over a broad temperature range
• A polymer with randomly coiled chains

Correct Answer: A material with atoms arranged in a regular, repeating three-dimensional pattern

Q2. What is a unit cell in crystallography?

• The smallest repeating structural unit that completely describes the crystal lattice
• The macroscopic crystal habit visible under a microscope
• A defect site where an atom is missing
• A measurement of crystal hardness

Correct Answer: The smallest repeating structural unit that completely describes the crystal lattice

Q3. How many Bravais lattices exist in three dimensions?

• 7
• 14
• 24
• 32

Correct Answer: 14

Q4. Which of the following is a characteristic of a primitive (P) unit cell?

• Contains lattice points only at the corners
• Has lattice points at corners and face centers
• Always represents the most compact packing
• Is only found in cubic crystals

Correct Answer: Contains lattice points only at the corners

Q5. What is the coordination number of atoms in a face-centered cubic (fcc) structure?

• 6
• 8
• 12
• 4

Correct Answer: 12

Q6. Which structure has a packing efficiency of approximately 74%?

• Simple cubic
• Body-centered cubic
• Face-centered cubic (ccp)
• Diamond cubic

Correct Answer: Face-centered cubic (ccp)

Q7. What do Miller indices (hkl) represent?

• The orientation of crystallographic planes relative to the unit cell axes
• The chemical composition of the unit cell
• The fracture toughness of a crystal
• The number of defects per unit volume

Correct Answer: The orientation of crystallographic planes relative to the unit cell axes

Q8. How are Miller indices determined for a plane that intercepts axes at a, b/2, and ∞?

• (1, 2, 0)
• (1, 0.5, ∞)
• (2, 1, 0)
• (1, 1, 1)

Correct Answer: (2, 1, 0)

Q9. What is Bragg’s law for X-ray diffraction?

• nλ = 2d sin θ
• E = hν
• ρ = m/V
• λ = hc/E

Correct Answer: nλ = 2d sin θ

Q10. Why is powder X-ray diffraction (PXRD) essential in pharmaceutical solids analysis?

• It identifies crystalline phases, polymorphs, and degree of crystallinity
• It measures only the particle size distribution
• It provides direct chemical assay of impurities
• It images internal microstructure like SEM

Correct Answer: It identifies crystalline phases, polymorphs, and degree of crystallinity

Q11. Which equation (name) is used to estimate crystallite size from XRD peak broadening?

• Van’t Hoff equation
• Scherrer equation
• Henderson–Hasselbalch equation
• Arrhenius equation

Correct Answer: Scherrer equation

Q12. Peak broadening in PXRD can be caused by which factors?

• Small crystallite size and microstrain
• Only instrument misalignment
• High purity and large crystals
• Absence of defects

Correct Answer: Small crystallite size and microstrain

Q13. What is polymorphism in pharmaceutical solids?

• The ability of a molecule to exist in more than one crystalline form
• The conversion of a crystal into an amorphous solid
• The formation of co-crystals only
• The hydration of a crystal by water molecules

Correct Answer: The ability of a molecule to exist in more than one crystalline form

Q14. Which polymorph is typically more soluble and often less stable?

• Thermodynamically stable polymorph
• Metastable polymorph
• Hydrated polymorph
• Covalent network polymorph

Correct Answer: Metastable polymorph

Q15. What distinguishes a hydrate from a solvate?

• Hydrate contains water molecules; solvate contains any solvent molecules
• Hydrate has stronger ionic bonds than solvates
• Hydrate is amorphous while solvate is crystalline
• Hydrate always decreases solubility, solvates increase it

Correct Answer: Hydrate contains water molecules; solvate contains any solvent molecules

Q16. How does crystallinity generally affect drug dissolution?

• Higher crystallinity usually decreases dissolution rate
• Higher crystallinity always increases dissolution rate
• Crystallinity has no effect on dissolution
• Only particle size matters, not crystallinity

Correct Answer: Higher crystallinity usually decreases dissolution rate

Q17. Which analytical technique is most used to detect polymorphic transitions by measuring heat flow?

• FTIR spectroscopy
• Differential scanning calorimetry (DSC)
• Gas chromatography
• UV-Vis spectroscopy

Correct Answer: Differential scanning calorimetry (DSC)

Q18. What is a point defect in a crystal?

• A localized imperfection such as a vacancy or interstitial
• A planar defect like a grain boundary
• A long-range dislocation line
• A surface imperfection only

Correct Answer: A localized imperfection such as a vacancy or interstitial

Q19. Which defect type involves a missing cation-anion pair in an ionic crystal?

• Frenkel defect
• Schottky defect
• Edge dislocation
• Screw dislocation

Correct Answer: Schottky defect

Q20. In a Frenkel defect, which process occurs?

• Atom vacates its lattice site and occupies an interstitial site
• Equal numbers of cations and anions are missing
• Vacancies form only at the surface
• Planar faults develop between grains

Correct Answer: Atom vacates its lattice site and occupies an interstitial site

Q21. What is the coordination number in the NaCl structure for each ion?

• 4
• 6
• 8
• 12

Correct Answer: 6

Q22. The CsCl structure differs from NaCl primarily by which feature?

• CsCl has coordination number 8 with a simple cubic arrangement for chloride
• CsCl is amorphous
• CsCl has a molecular crystal lattice
• CsCl contains water of crystallization always

Correct Answer: CsCl has coordination number 8 with a simple cubic arrangement for chloride

Q23. Which stacking sequence corresponds to hexagonal close packing (hcp)?

• ABCABC
• ABAB
• AABBCC
• ABCA

Correct Answer: ABAB

Q24. Which technique can provide quantitative phase analysis and unit cell parameters from powder diffraction data?

• Rietveld refinement
• Karl Fischer titration
• Optical microscopy
• Gel permeation chromatography

Correct Answer: Rietveld refinement

Q25. How is density (ρ) of a crystalline solid calculated from unit cell data?

• ρ = Z·M / (N_A·V_cell)
• ρ = M / Z
• ρ = V_cell / (Z·M)
• ρ = N_A / (Z·M·V_cell)

Correct Answer: ρ = Z·M / (N_A·V_cell)

Q26. What does Z represent in unit cell calculations?

• The number of formula units per unit cell
• The atomic number of the element
• The coordination number
• The unit cell edge length

Correct Answer: The number of formula units per unit cell

Q27. Which type of solid is characterized by directional covalent bonds and very high melting points (e.g., diamond, SiO2 network)?

• Molecular solids
• Ionic solids
• Covalent network solids
• Metallic solids

Correct Answer: Covalent network solids

Q28. How do crystal defects generally influence chemical reactivity and solubility?

• Defects increase surface energy and can increase solubility and reactivity
• Defects make crystals chemically inert
• Defects always decrease solubility
• Defects have no measurable effect on reactivity

Correct Answer: Defects increase surface energy and can increase solubility and reactivity

Q29. In crystallization, what distinguishes nucleation from crystal growth?

• Nucleation is formation of stable nuclei; growth is enlargement of those nuclei
• Nucleation requires solvents; growth occurs in vacuum only
• Nucleation happens only at low temperature; growth only at high temperature
• They are the same process with different names

Correct Answer: Nucleation is formation of stable nuclei; growth is enlargement of those nuclei

Q30. What is Ostwald’s rule of stages relevant to crystallization?

• The most stable phase always forms first
• The kinetically favored, less stable phase often forms first and may transform to a more stable phase
• Polymorphs never interconvert
• Hydrates form only after anhydrate forms

Correct Answer: The kinetically favored, less stable phase often forms first and may transform to a more stable phase

Q31. Which of the following best describes anisotropy in crystalline solids?

• Physical properties vary with crystallographic direction
• All physical properties are identical in every direction
• Optical properties are absent in crystals
• Anisotropy applies only to liquids

Correct Answer: Physical properties vary with crystallographic direction

Q32. What role does hydrogen bonding play in drug crystal packing?

• It stabilizes specific packing motifs and influences polymorphism and solubility
• It always destabilizes crystal structures
• It is irrelevant in organic molecular crystals
• It only affects metallic crystals

Correct Answer: It stabilizes specific packing motifs and influences polymorphism and solubility

Q33. Which technique complements PXRD to estimate degree of crystallinity by measuring melting enthalpy?

• Differential scanning calorimetry (DSC)
• Mass spectrometry
• Size-exclusion chromatography
• Atomic absorption spectroscopy

Correct Answer: Differential scanning calorimetry (DSC)

Q34. Which phenomenon describes the transformation of a solvated crystal into a different anhydrous form upon solvent loss?

• Desolvation or dehydration leading to polymorphic change
• Schottky defect formation
• Frenkel migration
• Thermal expansion without structural change

Correct Answer: Desolvation or dehydration leading to polymorphic change

Q35. What is the primary reason metastable polymorphs can be more bioavailable?

• They have higher lattice energy than stable forms
• They often possess higher solubility and faster dissolution rates
• They are always less soluble by definition
• They convert immediately to amorphous form in water

Correct Answer: They often possess higher solubility and faster dissolution rates

Q36. Which of the following is an example of a planar defect?

• Grain boundary
• Vacancy
• Edge dislocation
• Interstitial atom

Correct Answer: Grain boundary

Q37. How does temperature generally affect vacancy concentration in a crystal?

• Vacancy concentration decreases with increasing temperature
• Vacancy concentration increases with increasing temperature
• Temperature has no effect on vacancies
• Vacancies only form at absolute zero

Correct Answer: Vacancy concentration increases with increasing temperature

Q38. Which property is commonly used to distinguish crystalline from amorphous solids?

• Sharp, well-defined peaks in X-ray diffraction for crystalline solids
• Both show identical PXRD patterns
• Amorphous solids have multiple Bragg peaks
• Crystalline solids never melt

Correct Answer: Sharp, well-defined peaks in X-ray diffraction for crystalline solids

Q39. What is the reciprocal lattice used for in crystallography?

• To describe diffraction conditions and relate plane spacings to scattering vectors
• To calculate molecular weight from unit cell
• To measure particle size directly
• To model chemical reactivity of defects

Correct Answer: To describe diffraction conditions and relate plane spacings to scattering vectors

Q40. In powder diffraction indexing, what does a higher 2θ angle generally indicate about the corresponding d-spacing?

• The d-spacing is larger for higher 2θ
• The d-spacing is smaller for higher 2θ
• 2θ and d-spacing are unrelated
• d-spacing equals 2θ numerically

Correct Answer: The d-spacing is smaller for higher 2θ

Q41. Which crystallization additive is used to control crystal habit and morphology?

• Habit modifier or growth inhibitor
• Only pH buffers
• Only strong acids
• Nonpolar solvents only

Correct Answer: Habit modifier or growth inhibitor

Q42. What is the Scherrer equation dependent parameter that must be corrected for instrument broadening?

• Scattering factor
• Peak width (full width at half maximum, FWHM)
• Unit cell volume
• Molar mass

Correct Answer: Peak width (full width at half maximum, FWHM)

Q43. Which solid type typically has metallic bonding and delocalized electrons?

• Ionic solids
• Metallic solids
• Molecular solids
• Covalent network solids

Correct Answer: Metallic solids

Q44. How does pressure influence polymorphism in pharmaceutical solids?

• Pressure can stabilize denser polymorphs and induce phase transitions
• Pressure only affects amorphous solids
• Polymorph stability is independent of pressure
• Pressure always converts crystals to liquids

Correct Answer: Pressure can stabilize denser polymorphs and induce phase transitions

Q45. Which method is most suitable to detect very small populations of crystalline impurity in a bulk powder?

• Optical microscopy only
• High-resolution powder X-ray diffraction and careful peak analysis
• Simple melting point determination
• pH measurement

Correct Answer: High-resolution powder X-ray diffraction and careful peak analysis

Q46. What is the primary practical significance of polymorphism in drug development?

• Polymorphism has no commercial impact
• Different polymorphs can have different solubility, stability, and patentability implications
• All polymorphs are chemically identical and interchangeable without study
• Polymorphism only affects color, not performance

Correct Answer: Different polymorphs can have different solubility, stability, and patentability implications

Q47. What is the main difference between single-crystal XRD and powder XRD?

• Single-crystal XRD provides detailed atomic positions and bond geometry; powder XRD gives phase identification and unit cell parameters
• Powder XRD gives atomic positions; single-crystal only phases
• They are identical techniques with different names
• Single-crystal XRD cannot determine crystal symmetry

Correct Answer: Single-crystal XRD provides detailed atomic positions and bond geometry; powder XRD gives phase identification and unit cell parameters

Q48. Which of the following best describes cleavage in crystals?

• Tendency to break along specific crystallographic planes where bonding is weakest
• Random fracture with no preferred direction
• Formation of voids within the crystal lattice
• Recrystallization into a different polymorph

Correct Answer: Tendency to break along specific crystallographic planes where bonding is weakest

Q49. What is the effect of microparticulate crystalline defects on powder compaction and tableting?

• Defects can alter plasticity, compaction behavior, and mechanical strength of tablets
• Defects only influence color and taste
• Defects make powders impossible to compress
• There is no measurable effect on tablet properties

Correct Answer: Defects can alter plasticity, compaction behavior, and mechanical strength of tablets

Q50. Which pair contrasts vacancy and interstitial point defects?

• Vacancy: missing atom; Interstitial: extra atom in void space
• Vacancy: extra atom; Interstitial: missing atom
• Both are planar defects
• Neither affects diffusion properties

Correct Answer: Vacancy: missing atom; Interstitial: extra atom in void space

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com