Solid State Test

Result

Solid State Test - 53

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following is an example of metallic crystal solid?

A
$$C$$

B
$$Si$$

C
$$W$$

D
$$AgCl$$

Solution

Metalic crystals consists of metal cations surrounded by large number of mobile valence electrons, these electrons are also known as delocalised electrons, which do not belong to any one atom, but are capable of moving through the crystal.As a result metallic crystals are good conductors of electricity.
Example: gold-Au, tungsten-W
Question 2
1 / -0

When radius of central atom is double with respect to corner atoms, then find out % packing efficiency.

A
$$79$$%

B
$$90$$%

C
$$60$$%

D
$$65$$%

Solution

$$\sqrt { 3 } a=2r+2(2r)=6r$$
$$a=\cfrac { 6r }{ \sqrt { 3 } } =2\sqrt { 3 } r$$
$$P.F=\cfrac { \cfrac { 4 }{ 3 } \pi { r }^{ 3 }+\cfrac { 4 }{ 3 } \pi { (2r) }^{ 3 } }{ { a }^{ 3 } } \quad =\cfrac { \cfrac { 4 }{ 3 } \pi ({ r }^{ 3 }+{ 8r }^{ 3 }) }{ { (2\sqrt { 3 } r) }^{ 3 } } =\cfrac { 4\pi { \times 9r }^{ 3 } }{ 3\times 8\times 3\sqrt { 3 } { r }^{ 3 } } =\cfrac { \pi }{ 2\sqrt { 3 } } =0.906$$
% of packing efficiency $$=0.906\times 100=90.6$$%
Question 3
1 / -0

In a crystal, the atoms are located at the position of

A
zero potential energy

B
infinite potential energy

C
minimum potential energy

D
maximum potential energy

Solution
Question 4
1 / -0

A match box exhibits _____ geometry.

A
cubic

B
orthorhombic

C
triclinic

D
monoclinic

Solution
Question 5
1 / -0

Most crystals that show good cleavage because their atoms, ions or molecules are

A
weakly bonded together

B
strongly bonded together

C
spherically symmetrical

D
arranged in planes

Solution

Most crystals show good cleavage as their atoms, ions or molecule are arranged in planes which is due to flat crystal face.
Question 6
1 / -0

$$f-centre$$ is

A
Anion vacancy occupied by unpaired electron

B
Anion vacancy occupied by electron

C
Cation vacancy occupied by electron

D
Anion present in interstitial site

Solution

$$F-center$$ is unpaired $$e^{-}$$.
Question 7
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Which of the following statements about the interstitial compounds is incorrect?

A
They have higher melting points than the pure metal

B
They retain metallic conductivity

C
They are chemically reactive

D
They are much harder than the pure metal

Solution
Question 8
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Edge length of a cube is $$300\ pm$$. Its body diagonal would be

A
$$600\ pm$$

B
$$423\ pm$$

C
$$519.6\ pm$$

D
$$450.5\ pm$$

Solution

The length of the body diagonal $$= \sqrt {3}a$$

So the length of body diagonal $$= \sqrt {3} \times 300 = 519.6\ pm$$.
Question 9
1 / -0

Mostly crystals show good cleavage because their atoms, ions or molecules are:

A
Wealky bonded together

B
Strongly bonded together

C
Spherically symmetrical

D
Arranged in planes

Solution

Crystals show good cleavage because their constituent particles are arranged in planes.

Hence D is correct option
Question 10
1 / -0

There are three cubic unit cells $$A, B$$ and $$C$$. $$A$$ is FCC and all of its tetrahedral voids are also occupied. $$B$$ is also FCC and all of its octahedral voids are also occupied. $$C$$ is simple cubic and all of its cubic voids are also occupied. If voids in all unit cells are occupied by the spheres exactly at their limiting radius, then the order of packing efficiency would be

A
$$A< B< C$$

B
$$C< A< B$$

C
$$C< B< A$$

D
$$A< C< B$$

Solution