Solid State Test

Result

Solid State Test - 77

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Weekly Quiz Competition

Question 1
1 / -0

A compound has a BCC unit cell with an edge length of 10A. If the density is 2 $g/cm^{3}$ then the molar mass of the compound is

A
600

B
300

C
350

D
250

Solution
Question 2
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CCP is also called as :

A
FCC

B
BCC

C
Primitive

D
HCP

Solution
Question 3
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Sodium crystallises in bcc arrangement with the interfacial sepration between the atoms of the edge $53 pm$ . The density of the solid is :

A
$1.23 g/cc$

B
$485 g/cc$

C
$4.85 g/cc$

D
$123 g/cc$
Question 4
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Select the correct statement related to hexagonal close packing of identical spheres in three dimensions.

A
In one unit cell, there are 12 octahedral voids and all are completely inside the unit cell.

B
In one unit cell, there are six octahedral voids and all are completely inside the unit cell.

C
The number of atoms per unit cell in hcp are 12

D
Coordination number of every sphere is 8

Solution
Question 5
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In a cubic lattice if atoms are present only at all the corners and alternate face centres then the packing efficiency will be:

A
$74 \%$

B
$37\%$

C
$68\%$

D
Cannot be determined

Solution
Question 6
1 / -0

Edge length is 200 $\mathrm { pm }$ in body-centred unit cell what will be the radius of atom in pm?

A
139

B
150

C
86.6

D
93.4

Solution
Question 7
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Crystals of different ionic compounds having similar arrangement of ions as well as geometry are known:

A
Isomorphs

B
Isomers

C
Anomers

D
Isotopes
Question 8
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Which of the following is the only incorrect statement regarding amorphous solids?

A
On heating, they may become crystalline at some temperature

B
They may become crystalline on keeping for long time

C
Amorphous solids can be molded by heating

D
They are anisotropic in nature

Solution
Question 9
1 / -0

A lattice is defined as

A
the amount of energy required, per mole, to separate the ions from their lattice positions to an infinte distance in the gas phase

B
the distance separating the cations and anions

C
a set of all points with identical environments within crystal

D
the arrangement of electrons in various energy levels

Solution
Question 10
1 / -0

What is the packing efficiency of arrangement in a body centred unit cell?

A
$53.26\%$

B
$74.00\%$

C
$68.00\%$

D
$64.00\%$

Solution

Packing efficiency is defined as the percentage of space occupied by constituent particles packed inside the lattice.
Consider edge length is $a$
In BCC,
$AC=\sqrt{AB^2+BC^2}=\sqrt{a^2+a^2}=\sqrt2 a$

$AC=FD$

and $AF=\sqrt{AD^2+FD^2}=\sqrt{2a^2+a^2}=\sqrt{3}a$

Thus $\sqrt3 a=4r$ i.e., $a=\dfrac{4r}{\sqrt3}$
Volume of the unit cell= $a^3=\left(\dfrac{4r}{\sqrt3}\right)^3=\dfrac{64r^3}{3\sqrt3}$
Now, No. of spheres per unit cell= $8\times \dfrac18+1=1+1=2$
Thus volume of two spheres= $2\times \dfrac43 \pi r^3=\dfrac83 \pi r^3$
$\therefore \text{Packing efficiency}=\dfrac{\dfrac83 \pi r^3}{\dfrac{64}{3\sqrt3}r^3}=0.68$
Thus, $\%\text{Packing efficiency}=68\%$