Solid State Test

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Solid State Test - 39

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Weekly Quiz Competition

Question 1
1 / -0

The flame colours of metal ions are due to:

A
metal excess defect

B
metal deficiency defect

C
Schottky defect

D
Frenkel defect

Solution

The flame colours of metal ions are due to metal excess defect.
The free electrons can be excited to higher energy levels giving absorption spectra and as a consequence their compounds are coloured.
Question 2
1 / -0

The crystalline structure of $$NaCl$$ is:

A
hexagonal close packing

B
face centred cubic

C
square planar

D
body centred cubic

Solution

Sodium chloride $$(NaCl)$$ has face centred cube structure. It contains $$4Na^+$$ and $$4Cl^-$$ ions. Each $$Na^+$$ ion is surrounded by $$8Cl^-$$ ions and each $$Cl$$ ion is also surrounded by $$8Na^+$$ ions.
Question 3
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$$KBr$$ crystallises in $$NaCl$$ type of crystal lattice and its density is $$2.75 g/cm^3$$. Number of unit cells of $$KBr$$ present in a 1.00 $$mm^3$$ grain of $$KBr$$ are:

A
$$3. 6 \times 10^{18}$$

B
$$3. 6 \times 10^{16}$$

C
$$2. 34 \times 10^{23}$$

D
$$6.02 \times 10^{24}$$

Solution

In a unit cell of $$KBr,$$ there are four formula units of $$KBr$$ therefore,

Density $$(\rho)$$ $$=\dfrac {4 \times 119}{6.023\times 10^{23}a^3}= 2.75$$

$$a^3= 2.873 \times 10^{-22}\, cm^3$$

$$=2.873 \times 10^{-19}\, mm^3$$

Number of units cells per $$mm^3$$

$$\dfrac{1}{2.873 \times 10^{-19}}=\dfrac {10^{19}}{2.873}= 3.5 \times 10^{18}$$

Option A is correct.
Question 4
1 / -0

Interstitial hole is called tetrahedral because:

A
it is formed by four spheres

B
it is formed by four spheres and the centre of which forms a regular tetrahedron

C
coordination number of hole is 3

D
none of the above

Solution

The above fig shows a tetrahedral hole. It is the vacant space between four toucing sphere
Hence, interstitial holes(tetrahedral) are formed by four sphere.
Question 5
1 / -0

Fraction of the total octahedral voids occupied will be:

A
$$\dfrac {1}{2}$$

B
$$\dfrac {1}{4}$$

C
$$\dfrac {1}{8}$$

D
$$\dfrac {1}{6}$$

Solution

Fraction of the total octahedral voids occupied will be $$\displaystyle \dfrac {1}{2}$$
Note:
The space lattice given in the figure refers to spinel structure.
It is of type $$\displaystyle AB_2O_4$$. An example is $$\displaystyle MgAl_2O_4$$. Another example is ferrite $$\displaystyle ZnFe_2O_4$$

$$\displaystyle A^{2+}$$ occupies one eight of tetrahedral voids, oxide ions occupy one half of octahedral voids.
Question 6
1 / -0

In a face-centre cubic arrangement of A and B atoms whose A atoms are at the corner of the unit cell and B atoms at the face-centre, one of A atom is missing from one corner in the unit cell. The simplest formula of the compound is:

A
$$A_{24}B_7$$

B
$$A_7B_{24}$$

C
$$A_7B_4$$

D
$$AB_2$$

Solution

No. of atoms of $$A$$ from corners of unit cell $$=\displaystyle\frac{7}{8}$$
No. of atoms of $$B$$ from faces of unit cell$$=3$$
$$\therefore A:B=\displaystyle\frac{7}{8}:3=7:24$$
Thus, formula of the compound is $$A_7B_{24}$$.
Question 7
1 / -0

A metal crystallizes face-centered cubic lattice with the edge length of $$450\ pm$$. Molar mass of the metal is $$50\ g\ mol^{-1}$$. The density of metal will be:

A
$$2.64\ g\ cm^{-3}$$

B
$$3.64\ g\ cm^{-3}$$

C
$$4.64\ g\ cm^{-3}$$

D
$$2.68\ g\ cm^{-3}$$

Solution

$$Density (\rho) = \dfrac {ZM}{a^{3}\times N_{A}} = \dfrac {4\times 50}{(450\times 10^{-10})^{3} \times 6.023\times 10^{23}}$$ $$= 3.64\ g\ cm^{-3}$$.
Question 8
1 / -0

Arrangement of sulphide ions in zinc blende is

A
Simple cubic

B
HCP

C
BCC

D
FCC

Solution

Arrangement of sulphide ions $$(S^{2-})$$ in zinc blende $$(ZnS)$$ is fcc (occupy all corners and face centres) while $$Zn^{2+}$$ ion occupy alternate tetrahedral voids.
Question 9
1 / -0

Which of the following represents true statement?

A
Force of attraction between the molecules (inter molecular forces) in solids is very strong.

B
Force of attraction between the molecules (inter molecular forces) in solids is very weak.

C
Force of attraction between the molecules (inter molecular forces) in solids is either very strong or very weak.

D
There is no force of attraction between the molecules (inter molecular forces) in solids.

Solution

Force of attraction between the molecules (inter molecular forces) in solids is very strong. Due to this, the molecules are closely arranged and they are in-compressible.
Question 10
1 / -0

Iron crystallises in a bcc system with a lattice parameter of $$2.861\mathring { A } $$. Calculate the density of iron in the bcc system
[atomic weight of $$Fe=56,{ N }_{ A }=6.02\times { 10 }^{ 23 }{ mol }^{ -1 }$$].

A
$$7.94g\ m{ L }^{ -1 }$$

B
$$8.96g\ m{ L }^{ -1 }$$

C
$$2.78g\ m{ L }^{ -1 }$$

D
$$6.72g\ m{ L }^{ -1 }$$

Solution

$$d=\cfrac { ZM }{ { N }_{ A }{ a }^{ 3 } } $$ (for bcc, $$Z=2$$),

$$a= 2.861 \mathring {A}= 2.861 \times 10^{-8} cm$$

$${ d }_{ Fe }=\cfrac { (2)\times 56.0\ g\ { mol }^{ -1 } }{ \left( 6.02\times { 10 }^{ 23 }{ mol }^{ -1 } \right) { \left( 2.861\times { 10 }^{ -8 } \right) }^{ 3 }{ cm }^{ 3 } } $$

$$=7.94\ g/mL$$

Hence, the correct option is $$\text{A}$$

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Solid State Test - 39

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Solid State Test - 39

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Question 1

metal excess defect

metal deficiency defect

Schottky defect

Frenkel defect

Solution

Question 2

hexagonal close packing

face centred cubic

square planar

body centred cubic

Solution

Question 3

$$3. 6 \times 10^{18}$$

$$3. 6 \times 10^{16}$$

$$2. 34 \times 10^{23}$$

$$6.02 \times 10^{24}$$

Solution

Question 4

it is formed by four spheres

it is formed by four spheres and the centre of which forms a regular tetrahedron

coordination number of hole is 3

none of the above

Solution

Question 5

$$\dfrac {1}{2}$$

$$\dfrac {1}{4}$$

$$\dfrac {1}{8}$$

$$\dfrac {1}{6}$$

Solution

Question 6

$$A_{24}B_7$$

$$A_7B_{24}$$

$$A_7B_4$$

$$AB_2$$

Solution

Question 7

$$2.64\ g\ cm^{-3}$$

$$3.64\ g\ cm^{-3}$$

$$4.64\ g\ cm^{-3}$$

$$2.68\ g\ cm^{-3}$$

Solution

Question 8

Simple cubic

HCP

BCC

FCC

Solution

Question 9

Force of attraction between the molecules (inter molecular forces) in solids is very strong.

Force of attraction between the molecules (inter molecular forces) in solids is very weak.

Force of attraction between the molecules (inter molecular forces) in solids is either very strong or very weak.

There is no force of attraction between the molecules (inter molecular forces) in solids.

Solution

Question 10

$$7.94g\ m{ L }^{ -1 }$$

$$8.96g\ m{ L }^{ -1 }$$

$$2.78g\ m{ L }^{ -1 }$$

$$6.72g\ m{ L }^{ -1 }$$

Solution

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