Tag: the solid state

Questions Related to the solid state

$KBr$ shows, which of the following defects?

imperfections in solids solid state the solid state chemistry

  1. Frenkel defect

  2. Schottky defect

  3. Metal excess defect

  4. Metal deficiency

Show answer
Correct Option: B
Explanation:

Schottky defect is shown in highly ionic compound, highly coordinated compounds, and where there is only a small difference in sizes of cations and anions of which the compound lattice is composed.

Examples:- $NaCl, KCl, KBr, CsCl, AgBr$

In a non-stochiometric sample of cuprons sulphide, with the composition $Cu _{1.8}$, cupric ions are also present in the lattice. The mole % of $Cu^{2+}$ present in the copper content of the crystal is:

imperfections in solids solid state the solid state chemistry

  1. $99.9$%

  2. $11.11$%

  3. $88.88$%

  4. $18$%

Show answer
Correct Option: C
Explanation:

$180 \ Cu$ atoms are associated with $100 \ S$ atoms.

Let $x$ atoms be present as $Cu^{+}$
Total charge on $xCu^+$ and $(180-x)Cu^{2+}$ must be equal to total charge on $100 \ S^{2-}$ ions.
So, $x+2(180-x)=2 \times 100$
$x+360-2x=200$
$x=160$
% of $Cu^{+}$ ions $= \cfrac {160}{180} \times 100=88.9$%

If $NaCl$ is doped with ${ 10 }^{ -4 }mol$% of ${ SrCl } _{ 2 }$, the concentration of cation vacancies will be: $\left( { N } _{ A }=6.02\times { 10 }^{ 23 }{ mol }^{ -1 } \right) $:

imperfections in solids solid state the solid state chemistry

  1. $6.02\times { 10 }^{ 15 }{ mol }^{ -1 }$

  2. $6.02\times { 10 }^{ 16 }{ mol }^{ -1 }$

  3. $6.02\times { 10 }^{ 17 }{ mol }^{ -1 }$

  4. $6.02\times { 10 }^{ 14 }{ mol }^{ -1 }$

Show answer
Correct Option: C
Explanation:

$NaCl$ is doped with $10^{-4}$ $mol\%$ of $SrCl _2$, i.e., one mole of $NaCl$ will have $10^{-6}$ mol of $SrCl _2$

$\rightarrow Sr^{+2}$ will replace one cation.
Therefore, concentration of cation vacancy $=10^{-6}\times 6.022\times 10^{23}=6.022\times 10^{17}$ $mol^{-1}$

The mineral hawleyite, one form of $CdS$, crystallizes in one of the cubic lattices , with edge length 5.87 A The density of hawleyite is $ 4.63 g cm^{-3} $
In which cubic lattice does hawleyite crystallizes?

imperfections in solids solid state the solid state chemistry

  1. end centred cubic

  2. body centered cubic

  3. face centred cubic

  4. edge centred cubic

Show answer
Correct Option: C
Explanation:

Density of Howlegite $=4.63g/{ cm }^{ 3 }$  $(P)$

Edge length $={ 5.87A }^{ 0 }=5.87\times { 10 }^{ -8 }cm$ $(a)$
Density $\left( P \right) =\dfrac { z\times { a }^{ 3 }\times { N } _{ 0 } }{ M } $                                 $M=$ Molar mass of $cds=144g/mol$
$z=\dfrac { 4.63\times { \left( 5.87\times { 10 }^{ -8 } \right)  }^{ 3 }\times 6.02\times { 10 }^{ 23 } }{ 144 } $        $N=$ Avagadro Number $=6.023\times { 10 }^{ 23 }$
$=3.9\cong 4\quad \quad z=4$
$\therefore$   There are four formula units of cds present in on unit cell.
$\Rightarrow $  Face entered cubic lattice.

Which is correct statement?

imperfections in solids solid state the solid state chemistry

  1. Schottky defect occurs when radius of cation is smaller

  2. When temperature increases then number of defects decreases

  3. Frenkel defect occurs when radius of cation is smaller

  4. None of these

Show answer
Correct Option: B
Explanation:

As temperature and number of defects are inversely propotional, with increase in temperature number of defects decreases. 

In schottky effect, size of ions are almost same while in frenkel defect, size of cation is small .

(i) Frenkel defect create a vacancy defect at its original site and an interstitial defect at its new position.
(ii) Frenkel defect is stoichiometric point defect.
(iii) Frenkel defect is also called dislocation defect.
(iv) Silver halide shows Frenkel defect 
Select the correct statements :

imperfections in solids solid state the solid state chemistry

  1. $(ii),(iii),(iv)$ only

  2. $(i),(ii),(iii)$ only

  3. $(i),(ii),(iii),(iv)$

  4. $(i),(ii),(iv)$ only

Show answer
Correct Option: C

$NaCl$ shows Schottky defects and $AgCl$ Frenkel defects. Their electrical conductivity is due to ________.

imperfections in solids solid state the solid state chemistry

  1. motion of ions and not the motion of electrons

  2. notion of electrons and not the motion of ions

  3. lower coordination number of $NaCl$

  4. higher coordination number of $AgCl$

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Correct Option: A

Metallic or non-stoichiometric (or interstitial) hydrides are formed by:

imperfections in solids solid state the solid state chemistry

  1. Many d-block and f-block elements.

  2. Many s-block elements

  3. Many p-block elements

  4. None of these

Show answer
Correct Option: A

Calculate the dencity of NaCl type ionic solid AB($M _{w}$=60) in $gm/CM^{3}$ if shortest distance between two nearest neighbours is 100 pm &solid having $20\%$ schottky defect$(N _{A}=6\times10^{23}$)

imperfections in solids solid state the solid state chemistry

  1. 10

  2. 20

  3. 30

  4. 40

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Correct Option: C

When NaCl is doped with ${ 10 }^{ -3 }$ mole % of Sr${ Cl } _{ 2 }$, what is the number of cationic vacancies?

imperfections in solids solid state the solid state chemistry

  1. ${ 10 }^{ -5 }\times { N } _{ A }$

  2. ${ 10 }^{ -7 }\times { N } _{ A }$

  3. 6.022$\times{ 10 }^{8 }{ N } _{ A }$

  4. None of these

Show answer
Correct Option: C