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Class Twelve Chemistry

Solid State-NCERT Exemplar Problems & Solution

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MCQs

Question: 1. Which of the following conditions favours the existence of a substance in the solid state?

(a) High temperature

(b) Low temperature

(c) High termal energy

(d) Weak cohesive forces

Answer: (b) Low temperature

Explanation:

In solid state substance exists due to slow molecular motion and strong cohesive forces at low temperature. At low temperature these two forces, i.e. slow molecular motion and strong cohesive forces are responsible to hold the constituents particles together.

This makes the existence of substance at low temperature in solid states.

Question: 2. Which of the following is not a characteristic of a crystalline solid?

(a) Definite and characteristic heat of fusion

(b) Isotropic nature

(c) A regular periodically repeated pattern of arrangement of constituent particles in the entire crystal

(d) A true solid

Answer: (b) Isotropic nature

Explanation

Crystalline solids are anisotropic in nature and not Isotropic in nature. Crystalline solids shows definite and characteristic heat of fusion, a regular periodically repeated pattern of arrangement of constituent particles in the entire crystal and crystalline is a true solid.

Isoropic nature is the characteristic of Amorphous solid.

Question: 3. Which of the following is an amorphous solid?

(a) Graphite (C)

(b) Quartz glass `(SiO_2)`

(c) Chrome alum

(d) Silicon carbide (SiC)

Answer: (b) Quartz glass `(SiO_2)`

Explanation

In the given options, only Quartz glass `(SiO_2)` is the example of amorphous solid. As Quartz glass `(SiO_2)` has short range order of constituent particles. However Quarz is an crystalline solid.

Rest options, Graphite (C), Chrome alum, and Silicon carbide (SiC) are the examples of crystalline solid.

Question: 4. Which of the following arrangement shows schematic alignment of magnetic moments of antiferromagnetic substances?

(a) class 12 exemplar problems and solution solid state1

(b) class 12 exemplar problems and solution solid state2

(c) class 12 exemplar problems and solution solid state3

(d) class 12 exemplar problems and solution solid state4

Answer: (d) class 12 exemplar problems and solution solid state4

Explanation

Antiferromagnetic substances has oppositely oriented domain structure. Oppositely domain structure in antiferromagnetic substances cancels each other’s magnetic field.

Question: 5. Which of the following is true about the value of refractive index of quartz glass?

(a) Same in all directions

(b) Different in different directions

(c) Cannot be measured

(d) Always zero

Answer: (a) Same in all directions

Explanation

Quartz is an amorphous solid and have short range order of constituent particles and thus, and tus value of refractive index of quartz glass can be measured and is same in all directions.

Question: 6. Which of the following statement is not true about amorphous solid?

(a) On heating they may become crystalline at certain temperature

(b) They may become crystalline on keeping for long time

(c) Amorphous solids can be moulded by heating

(d)They are anisotropic in nature.

Answer: (d)They are anisotropic in nature.

Explanation

Amorphous solids are isotropic in nature and not anisotropic.

Question: 7. The sharp melting point of crystalline solids is due to …………….

(a) a regular arrangement of constituent particles observed over a short distance in the crystalline lattice

(b) a regular arrangement of constituent particles observed over a long distance in the crystal lattice

(c) same arrangement of constituent particles in different directions

(d) different arrangement of constituent particles in different directions.

Answer: (b) a regular arrangement of constituent particles observed over a long distance in the crystal lattice

Explanation

Crystalline solids have sharp melting point because they have a regular arrangement of constituent particles observed over a long distance in the crystalline lattice.

Question: 8. Iodine molecules are held in the crystals lattice by ……………..

(a) London forces

(b) Dipole – dipole interactions

(c) Covalent bonds

(d) Coulombic forces

Answer: (a) London forces

Explanation

In iodine molecules are a non polar molecular solid and constituents particles are held together with London forces or dispersion forces.

Question: 9. Which of the following is a network solid?

(a) `SO_2` (solid)

(b) `I_2`

(c) Diamond

(d) `H_2O` (ice)

Answer: (c) Diamond

Explanation

Atoms of diamond are held together with covalent bond and form a giant molecule that’s why diamond is a network solid.

Question: 10. Which of the following solids is not an electrical conductor?

(1) Mg(s)

(2) TiO(s)

(3) `I_2` (s)

(4) `H_2O` (s)

(a) only 1

(b) Only 2

(c) 3 and 4

(d) 2, 3 and 4

Answer: (c) 3 and 4

Explanation

Iodine is a non polar molecular solid and hence non-conductor of electricity. In solid water (ice), molecules are bonded together because of hydrogen bond and show non-ionic nature, thus water in solid state is also non conductor of electricity.

Question: 11. Which of the following is not the characteristic of ionic solids?

(a) Very low value of electrical conductivity in the molten state

(b) Brittle nature

(c) Very strong forces of interactions

(d) Anisotropic nature

Answer: (a) Very low value of electrical conductivity in the molten state

12. Graphite is a good conductor of electricity due to the presence of __________.

(i) lone pair of electrons

(ii) free valence electrons

(iii) cations

(iv) anions

Answer: (ii) free valence electrons

13. Which of the following oxides behaves as conductor or insulator depending upon temperature?

(i) TiO

(ii) `SiO_2`

(iii) `TiO_3`

(iv) MgO

Answer: (iii) `TiO_3`

14. Which of the following oxides shows electrical properties like metals?

(i) `SiO_2`SiO_2`

(ii) MgO

(iii) `SO_2(s)`

(iv) `CrO_2`

Answer: (iv) `CrO_2`

15. The lattice site in a pure crystal cannot be occupied by _________.

(i) molecule

(ii) ion

(iii) electron

(iv) atom

Answer: (iii) electron

16. Graphite cannot be classified as __________.

(i) conducting solid

(ii) network solid

(iii) covalent solid

(iv) ionic solid

Answer: (iv) ionic solid

17. Cations are present in the interstitial sites in __________.

(i) Frenkel defect

(ii) Schottky defect

(iii) Vacancy defect

(iv) Metal deficiency defect

Answer: (i) Frenkel defect

18. Schottky defect is observed in crystals when __________.

(i) some cations move from their lattice site to interstitial sites.

(ii) equal number of cations and anions are missing from the lattice.

(iii) some lattice sites are occupied by electrons.

(iv) some impurity is present in the lattice.

Answer: (ii) equal number of cations and anions are missing from the lattice.

19. Which of the following is true about the charge acquired by p-type semiconductors?

(i) positive

(ii) neutral

(iii) negative

(iv) depends on concentration of p impurity

Answer: (ii) neutral

20. To get a n-type semiconductor from silicon, it should be doped with a substance with valence__________.

(i) 2

(ii) 1

(iii) 3

(iv) 5

Answer: (iv) 5

21. The total number of tetrahedral voids in the face centred unit cell is __________.

(i) 6

(ii) 8

(iii) 10

(iv) 12

Answer: (ii) 8

22. Which of the following point defects are shown by AgBr(s) crystals?

(A) Schottky defect

(B) Frenkel defect

(C) Metal excess defect

(D) Metal deficiency defect

(i) (A) and (B)

(ii) (C) and (D)

(iii) (A) and (C)

(iv) (B) and (D)

Answer: (i) (A) and (B)

23. In which pair most efficient packing is present?

(i) hcp and bcc

(ii) hcp and ccp

(iii) bcc and ccp

(iv) bcc and simple cubic cell

Answer: (ii) hcp and ccp

24. The percentage of empty space in a body centred cubic arrangement is ________.

(i) 74

(ii) 68

(iii) 32

(iv) 26

Answer: (iii) 32

25. Which of the following statement is not true about the hexagonal close packing?

(i) The coordination number is 12.

(ii) It has 74% packing efficiency.

(iii) Tetrahedral voids of the second layer are covered by the spheres of the third layer.

(iv) In this arrangement spheres of the fourth layer are exactly aligned with those of the first layer.

Answer: (iv) In this arrangement spheres of the fourth layer are exactly aligned with those of the first layer.

26. In which of the following structures coordination number for cations and anions in the packed structure will be same?

(i) `Cl^-` ion form fcc lattice and `Na^+` ions occupy all octahedral voids of the unit cell.

(ii) `Ca^(2+)`Ca2+ ions form fcc lattice and F – ions occupy all the eight tetrahedral voids of the unit cell.

(iii) `O^(2-)` ions form fcc lattice and Na+ ions occupy all the eight tetrahedral voids of the unit cell.

(iv) `S^(2-)` ions form fcc lattice and Zn2+ ions go into alternate tetrahedral voids of the unit cell.

Answer: (i) `Cl^-` ion form fcc lattice and `Na^+` ions occupy all octahedral voids of the unit cell.

27. What is the coordination number in a square close packed structure in two dimensions?

(i) 2

(ii) 3

(iii) 4

(iv) 6

Answer: (iii) 4

28. Which kind of defects are introduced by doping?

(i) Dislocation defect

(ii) Schottky defect

(iii) Frenkel defects

(iv) Electronic defects

Answer: (iv) Electronic defects

29. Silicon doped with electron-rich impurity forms ________.

(i) p-type semiconductor

(ii) n-type semiconductor

(iii) intrinsic semiconductor

(iv) insulator

Answer: (ii) n-type semiconductor

30. Which of the following statements is not true?

(i) Paramagnetic substances are weakly attracted by magnetic field.

(ii) Ferromagnetic substances cannot be magnetised permanently.

(iii) The domains in antiferromagnetic substances are oppositely oriented with respect to each other.

(iv) Pairing of electrons cancels their magnetic moment in the diamagnetic substances.

Answer: (ii) Ferromagnetic substances cannot be magnetised permanently.

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