Select the correct option based on statements below:

Assertion (A): The stability of a crystal is reflected by the magnitude of its melting point.
Reason (R): Greater the intermolecular forces of attraction, the higher will be the stability and melting point of the substance.
 
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true but (R) is false.
4. Both (A) and (R) are false.
Subtopic:  Introduction & Crystal System |
 87%
From NCERT
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The coordination number of a square close-packed structure in two dimensions is -

1. 2

2. 3

3. 4

4. 6

Subtopic:  Introduction & Crystal System |
 76%
From NCERT
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An example of amorphous solid among the following is -

1. Graphite (C)

2. Quartz glass (SiO2)

3. Chrome alum

4. Silicon carbide (SiC)

Subtopic:  Introduction & Crystal System |
 77%
From NCERT
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 The pair having only molecular solids among the following is -

1. Brass and SiC

2. Ammonium phosphate (NH4)3PO4

3. SiC and plastic 

4. Tetra phosphorus decaoxide (P4O10) and I2

Subtopic:  Introduction & Crystal System |
 67%
From NCERT
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The correct order of the packing efficiency in different types of unit cells is-

1.  Fcc < Bcc < Simple cubic

2.  Fcc > Bcc > Simple cubic

3.  Fcc < Bcc > Simple cubic

4.  Bcc < Fcc > Simple cubic

Subtopic:  Density & Packing Fraction |
 87%
From NCERT
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The most efficient packing is present in -

1. HCP and BCC

2. HCP and CCP

3. BCC and CCP

4. BCC and Simple cubic cell

Subtopic:  Density & Packing Fraction |
 82%
From NCERT
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An element has a body-centered cubic (BCC) structure with a cell edge of 288 pm. The atomic radius is:

1. 24×288 pm

2. 43×288 pm

3. 42×288 pm

4. 34×288 pm

Subtopic:  Introduction & Crystal System | Density & Packing Fraction |
 82%
From NCERT
NEET - 2020
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The formula of nickel oxide with metal deficiency defect in its crystal is Ni0.98O. The crystal contains Ni2+ and Ni3+ ions. The fraction of nickel existing as Ni2+ ions in the crystal is-

1. 0.96

2. 0.04

3. 0.50

4. 0.31

Subtopic:  Density & Packing Fraction |
 76%
From NCERT
NEET - 2019
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A metal has a fcc lattice. The edge length of the unit cell is 404 pm. The density of the metal is 2.72 g cm–3. The molar mass of the metal is:
(NA Avogadro's constant = 6.02 × 1023 mol–1)
1. 30 g mol–1
2. 27 g mol–1
3. 20 g mol–1
4. 40 g mol–1
Subtopic:  Density & Packing Fraction |
 75%
From NCERT
AIPMT - 2013
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The anions (A) form hexagonal closest packing and atoms (C) occupy only 2/3 of octahedral voids in it. The general formula of the compound is-
1. CA
2. CA2
3. C2A3
4. C3A2

Subtopic:  Density & Packing Fraction |
 74%
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