Chemistry 12 Chapter 1 Exemplar Solutions State Solid State Part 3

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Question 26:

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

(i) form lattice and ions occupy all octahedral voids of the unit cell.

(ii) ions form lattice and occupy all the eight tetrahedral voids of the unit cell.

(iii) ions form lattice and ions occupy all the eight tetrahedral voids of the unit cell.

(iv) ions form lattice and ions go into alternate tetrahedral voids of the unit cell.

Answer: (i)

Question 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)

Question 28:

Which kind of defects are introduced by doping?

(i) Dislocation defect

(ii) Schottky defect

(iii) Frenkel defects

(iv) Electronic defects

Answer: (iv)

Question 29:

Silicon doped with electron-rich impurity forms ________.

(i) p-type semiconductor

(ii) n-type semiconductor

(iii) Intrinsic semiconductor

(iv) Insulator

Answer: (ii)

Question 30:

Which of the following statements is not true?

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

(ii) Ferromagnetic substances cannot be magnetized 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)

Question 31:

Which of the following is not true about the ionic solids?

(i) Bigger ions form the close packed structure.

(ii) Smaller ions occupy either the tetrahedral or the octahedral voids depending upon their size.

(iii) Occupation of all the voids is not necessary.

(iv) The fraction of octahedral or tetrahedral voids occupied depends upon the radii of the ions occupying the voids.

Answer: (iv)

Question 32:

A ferromagnetic substance becomes a permanent magnet when it is placed in a magnetic field because ________.

(i) All the domains get oriented in the direction of magnetic field.

(ii) All the domains get oriented in the direction opposite to the direction of magnetic field.

(iii) Domains get oriented randomly.

(iv) Domains are not affected by magnetic field.

Answer: (i)

Question 33:

The correct order of the packing efficiency in different types of unit cells is ________.

(i)

(ii)

(iii)

(iv)

Answer: (ii)

Question 34:

Which of the following defects is also known as dislocation defect?

(i) Frenkel defect

(ii) Schottky defect

(iii) Non-stoichiometric defect

(iv) Simple interstitial defect

Answer: (i)

Question 35:

In the cubic close packing, the unit cell has ________.

(i) 4 tetrahedral voids each of which is shared by four adjacent unit cells.

(ii) 4 tetrahedral voids within the unit cell.

(iii) 8 tetrahedral voids each of the, which is shared by four adjacent unit cells.

(iv) 8 tetrahedral voids within the unit cells.

Answer: (iv)

Question 36:

The edge lengths of the unit cells in terms of the radius of spheres constituting and simple cubic unit cell are respectively________.

(i)

(ii)

(iii)

(iv)

Answer: (i)

Question 37:

Which of the following represents correct order of conductivity in solids?

(i)

(ii)

(iii)

(iv)

Answer: (i)

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