MCQs on Solid State – CBSE Class 12 Chemistry

Physical Chemistry – MCQ Titles (NCERT Based)
Course: CBSE Class 12 Chemistry – MCQs with Answers and Explanations

The following 50 NCERT-aligned MCQs are strictly prepared as per the CBSE Class 12 Chemistry syllabus. Questions are structured to build conceptual clarity, numerical confidence, and board-exam readiness, with accurate answers and detailed explanations.

Section A: Basic Concepts of Solid State

1. Which of the following best defines a solid?

A. Fixed volume but no definite shape
B. Definite shape and definite volume
C. No definite shape or volume
D. Highly compressible state

Correct Answer: B
Explanation: Solids possess strong intermolecular forces, resulting in a fixed shape and fixed volume.

2. Which type of solid lacks long-range order?

A. Crystalline solids
B. Metallic solids
C. Ionic solids
D. Amorphous solids

Correct Answer: D
Explanation: Amorphous solids do not have a regular arrangement of particles over long distances.

3. Glass is an example of:

A. Crystalline solid
B. Ionic solid
C. Amorphous solid
D. Metallic solid

Correct Answer: C
Explanation: Glass shows irregular arrangement of particles and no sharp melting point.

4. Which property is common to crystalline solids?

A. Isotropy
B. Irregular shape
C. Anisotropy
D. Random particle arrangement

Correct Answer: C
Explanation: Crystalline solids show anisotropy, meaning physical properties vary with direction.

5. Sharp melting point is a characteristic of:

A. Amorphous solids
B. Colloids
C. Crystalline solids
D. Polymers

Correct Answer: C
Explanation: Crystalline solids melt at a definite temperature due to uniform lattice structure.

Section B: Types of Crystalline Solids

6. Which solid is held together by electrostatic forces?

A. Molecular solid
B. Covalent solid
C. Ionic solid
D. Metallic solid

Correct Answer: C
Explanation: Ionic solids consist of oppositely charged ions held by strong electrostatic forces.

7. Diamond belongs to which category?

A. Molecular solid
B. Ionic solid
C. Metallic solid
D. Covalent solid

Correct Answer: D
Explanation: Diamond is a covalent (network) solid with strong covalent bonds throughout.

8. Which solid is soft and has low melting point?

A. Ionic solid
B. Metallic solid
C. Covalent solid
D. Molecular solid

Correct Answer: D
Explanation: Molecular solids are held by weak van der Waals forces.

9. Graphite conducts electricity because:

A. It has free ions
B. It contains delocalized electrons
C. It is metallic
D. It has ionic bonds

Correct Answer: B
Explanation: Graphite has delocalized π-electrons that allow electrical conduction.

10. Which solid is malleable and ductile?

A. Ionic solid
B. Molecular solid
C. Metallic solid
D. Covalent solid

Correct Answer: C
Explanation: Metallic solids have mobile electrons that allow deformation without breaking bonds.

Section C: Crystal Lattices and Unit Cells

11. A unit cell is defined as:

A. The smallest particle of a solid
B. The smallest repeating unit of a crystal lattice
C. A group of atoms
D. A molecule in a solid

Correct Answer: B
Explanation: Repetition of unit cells in space generates the entire crystal lattice.

12. Number of atoms per unit cell in simple cubic lattice is:

A. 1
B. 2
C. 4
D. 6

Correct Answer: A
Explanation: Eight corner atoms contribute 1/8 each → total = 1 atom.

13. Number of atoms per unit cell in body-centered cubic lattice is:

A. 1
B. 2
C. 4
D. 6

Correct Answer: B
Explanation: 1 atom from corners + 1 atom at body center = 2 atoms.

14. Number of atoms per unit cell in face-centered cubic lattice is:

A. 2
B. 3
C. 4
D. 6

Correct Answer: C
Explanation: 8 corners (1 atom) + 6 face centers (3 atoms) = 4 atoms.

15. Coordination number of simple cubic structure is:

A. 4
B. 6
C. 8
D. 12

Correct Answer: B
Explanation: Each atom touches 6 nearest neighbors.

Section D: Packing Efficiency and Voids

16. Packing efficiency of simple cubic lattice is approximately:

A. 52%
B. 68%
C. 74%
D. 32%

Correct Answer: A
Explanation: Simple cubic has large empty spaces, giving low packing efficiency.

17. Packing efficiency of face-centered cubic lattice is:

A. 52%
B. 68%
C. 74%
D. 90%

Correct Answer: C
Explanation: FCC structure has the highest packing efficiency (74%).

18. Tetrahedral void is surrounded by:

A. 3 atoms
B. 4 atoms
C. 6 atoms
D. 8 atoms

Correct Answer: B
Explanation: A tetrahedral void is formed by four closely packed atoms.

19. Number of tetrahedral voids per atom in close packing is:

A. 1
B. 2
C. 4
D. 6

Correct Answer: B
Explanation: In close-packed structures, tetrahedral voids = 2 × number of atoms.

20. Octahedral void is surrounded by:

A. 4 atoms
B. 6 atoms
C. 8 atoms
D. 12 atoms

Correct Answer: B
Explanation: Six atoms form an octahedral void.

Section E: Density and Radius Calculations

21. Density of a unit cell depends on:

A. Atomic radius only
B. Number of atoms and edge length
C. Shape of crystal
D. Temperature only

Correct Answer: B
Explanation: Density = (Z × molar mass) / (Nₐ × a³).

22. Relation between edge length (a) and atomic radius (r) for simple cubic is:

A. a = 2r
B. a = 4r
C. a = √2 r
D. a = √3 r

Correct Answer: A
Explanation: Atoms touch along the edge in simple cubic lattice.

23. Relation between edge length and radius in FCC lattice is:

A. a = 2r
B. a = 4r
C. a = √2 r
D. a = 2√2 r

Correct Answer: D
Explanation: In FCC, atoms touch along face diagonal.

24. Relation between edge length and radius in BCC lattice is:

A. a = 2r
B. a = 4r/√3
C. a = √2 r
D. a = √3 r

Correct Answer: B
Explanation: Atoms touch along the body diagonal.

25. If Z increases, density of crystal:

A. Decreases
B. Remains constant
C. Increases
D. Becomes zero

Correct Answer: C
Explanation: Density is directly proportional to number of atoms per unit cell.

Section F: Defects in Solids

26. Schottky defect is observed in:

A. Covalent solids
B. Metallic solids
C. Ionic solids
D. Molecular solids

Correct Answer: C
Explanation: Equal number of cations and anions are missing from lattice points.

27. Frenkel defect involves:

A. Missing ions
B. Displaced ions
C. Extra ions
D. Electron holes

Correct Answer: B
Explanation: An ion moves from its lattice position to an interstitial site.

28. Which defect lowers density of a crystal?

A. Frenkel defect
B. Schottky defect
C. Interstitial defect
D. Electronic defect

Correct Answer: B
Explanation: Missing ions reduce mass without changing volume.

29. Non-stoichiometric defects are common in:

A. Molecular solids
B. Ionic solids
C. Metallic solids
D. Covalent solids

Correct Answer: B
Explanation: Especially common in transition metal oxides.

30. F-centres are related to:

A. Missing cations
B. Missing anions with trapped electrons
C. Extra atoms
D. Frenkel defects

Correct Answer: B
Explanation: Trapped electrons in anion vacancies impart color to crystals.

Section G: Electrical Properties and Applications

31. Which solid acts as an insulator?

A. Metallic solid
B. Ionic solid (solid state)
C. Graphite
D. Semiconductor

Correct Answer: B
Explanation: In solid state, ions are not free to move.

32. Conductivity of metals is due to:

A. Ions
B. Protons
C. Delocalized electrons
D. Holes

Correct Answer: C
Explanation: Free electrons move under applied electric field.

33. Semiconductors show increased conductivity with:

A. Decrease in temperature
B. Increase in temperature
C. Pressure
D. Density

Correct Answer: B
Explanation: More electrons gain energy to cross band gap at higher temperature.

34. n-type semiconductor is doped with:

A. Trivalent impurity
B. Pentavalent impurity
C. Divalent impurity
D. Monovalent impurity

Correct Answer: B
Explanation: Pentavalent atoms donate extra electrons.

35. p-type semiconductor contains:

A. Excess electrons
B. Excess holes
C. Neutral atoms
D. Extra neutrons

Correct Answer: B
Explanation: Trivalent doping creates electron deficiency (holes).

Section H: Miscellaneous and Exam-Oriented MCQs

36. Polymorphism refers to:

A. Same crystal in different forms
B. Different substances in same form
C. Same solid in different forms
D. Amorphous nature

Correct Answer: C
Explanation: Existence of solid in more than one crystalline form.

37. Allotropy is shown by:

A. Ionic solids
B. Metals only
C. Elements
D. Compounds

Correct Answer: C
Explanation: Different structural forms of same element.

38. Which solid has highest melting point?

A. Ice
B. NaCl
C. Diamond
D. Iodine

Correct Answer: C
Explanation: Diamond has strong covalent network structure.

39. Bravais lattices in three dimensions are:

A. 7
B. 10
C. 12
D. 14

Correct Answer: D
Explanation: There are 14 Bravais lattices in 3D space.

40. Which property is direction-dependent?

A. Isotropy
B. Density
C. Anisotropy
D. Compressibility

Correct Answer: C
Explanation: Crystalline solids show anisotropic behavior.

41. Which solid is brittle?

A. Metallic solid
B. Ionic solid
C. Molecular solid
D. Amorphous solid

Correct Answer: B
Explanation: Ionic solids break under stress due to repulsion of like charges.

42. Edge length of unit cell is measured in:

A. cm
B. mm
C. pm or Å
D. m

Correct Answer: C
Explanation: Atomic-scale dimensions are measured in picometers or angstroms.

43. Which defect does not affect density?

A. Frenkel defect
B. Schottky defect
C. Vacancy defect
D. Interstitial defect

Correct Answer: A
Explanation: No ions are lost, only displaced.

44. Coordination number of FCC lattice is:

A. 6
B. 8
C. 10
D. 12

Correct Answer: D
Explanation: Each atom touches 12 nearest neighbors.

45. Void fraction is minimum in:

A. Simple cubic
B. BCC
C. FCC
D. Amorphous solids

Correct Answer: C
Explanation: FCC has maximum packing efficiency.

46. Which solid shows diffuse X-ray diffraction pattern?

A. Crystalline solid
B. Ionic solid
C. Metallic solid
D. Amorphous solid

Correct Answer: D
Explanation: Lack of long-range order causes diffuse pattern.

47. NaCl crystal shows which structure?

A. Simple cubic
B. BCC
C. FCC
D. Hexagonal

Correct Answer: C
Explanation: NaCl has FCC arrangement of ions.

48. Which is a covalent network solid?

A. NaCl
B. Graphite
C. Ice
D. CO₂

Correct Answer: B
Explanation: Graphite has strong covalent bonds in layers.

49. Which defect is also called dislocation defect?

A. Point defect
B. Line defect
C. Frenkel defect
D. Schottky defect

Correct Answer: B
Explanation: Line defects involve irregularity along a line in lattice.

50. Which property helps identify crystalline nature?

A. Color
B. Shape
C. Sharp melting point
D. Odor

Correct Answer: C
Explanation: Crystalline solids melt at a fixed temperature.

✅ End of NCERT-Based MCQs on Solid State