# Aluminum crystallizes in a cubic close-packed structure. It's metallic radius is 125 pm. The number of unit cells in 1.00 cm3 of aluminum are :  1. 2.27 x 1022 2. 354 x 1022 3. 4.54 x 1022 4. 127 x 1020

Subtopic:  Introduction & Crystal System |
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NaCl is doped with 10−3 mol % of SrCl2. The number of cation vacancies post doping would be -

1. 4.022 × 108

2. 5.022 × 1018

3. 6.022 × 1018

4. 7.022 × 108

Subtopic:  Imperfections in Solids & Semiconductors |
85%
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The relation between the atomic mass of unknown metal with density and the dimension of its unit cell is given by  :

(Given: All the cell edge lengths are equal)

1. $$m \ = \ \frac{\rho a^{3}N_{A}}{Z}$$
2. $$m \ = \ \rho a^{3}N_{A}Z$$
3. $$m \ = \ \frac{Z}{\rho a^{3}N_{A}}$$
4. $$m \ = \ \frac{ZN_{A}}{a^{3}\rho}$$

Subtopic:  Density & Packing Fraction |
84%
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The correct statement among the following is -

 1 Semiconductors have a small energy gap between the valence band and the conduction band. 2 Conductors have overlapped valence band and conduction band. 3 Insulators have a large energy gap between the valence band and conduction band. 4 All of the above.

Subtopic:  Imperfections in Solids & Semiconductors |
92%
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A defect that has an equal number of missing cations and anions is:

1. Schottky defect.

2. Frenkel defect.

3. Both (1) and (2)

4. None of the above.

Subtopic:  Imperfections in Solids & Semiconductors |
82%
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The magnetic substances that have lesser magnetic moment than expected is known as -

1. Paramagnetic.

2. Ferrimagnetic.

3. Antiferromagnetic.

4. None of the above.

Subtopic:  Magnetic Behaviour of an Element/Compound |
50%
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(i) Ge is doped with In

(ii) Si is doped with B.

The semiconductors formed in the above cases are :

1. (i) n-type semiconductor  (ii) p-type semiconductor .

2. (i) p-type semiconductor  (ii) n-type semiconductor .

3. p-type semiconductor in both the cases.

4. n-type semiconductor in both the cases.

Subtopic:  Imperfections in Solids & Semiconductors |
66%
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Higher conductivity of p-type and n-type semiconductors is due to:

 1 Increase in the number of positive holes and mobile electrons respectively. 2 Increase in the number of electrons in both types of semiconductors. 3 Increase in the number of positive-holes in both types of semiconductors. 4 None of the above.
Subtopic:  Imperfections in Solids & Semiconductors |
82%
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If the radius of the octahedral void is r and the radius of the atoms in close packing is R, the relation between r and R would be -

1. r = 0.114R

2. r = 0.444R

3. r = 1.414R

4. r = 0.414R

Subtopic:  Voids, Radius Ratio & Coordination Number |
66%
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Niobium crystallizes in body-centred cubic structure. If the density is 8.55 g cm−3, the atomic radius of niobium (atomic mass 93 u) is -

1. 13.32 nm

2. 12.32 nm

3. 14.32 nm

4. 15.32 nm

Subtopic:  Density & Packing Fraction |
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