Tag: imperfections in solids

Questions Related to imperfections in solids

Green $Cr^{3+}$ changes to yellow ${ Cro } _{ 4 }^{ 2- }$ on boiling with

imperfections in solids solid state the solid state chemistry

  1. Aklaline $H _2O _2$

  2. Acidified for $H _2O _2$

  3. Both (1) and (2)

  4. None of these

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Correct Option: C

The type of defect in $Nacl$ crystal will be -

imperfections in solids solid state the solid state chemistry

  1. point defect

  2. interstitial will be

  3. vacancy defect

  4. impurity defect

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Correct Option: C

If 1 mole of NaCl is doped with $10^{-3}$ mole of $SrCl _2$. What is the number of cationic  vacancies per mole of NaCl ?

imperfections in solids solid state the solid state chemistry

  1. $10^{-3}\, mole ^{-1}$

  2. $6.02\times 10^{18}\, mole ^{-1}$

  3. $10^{50}\, mole ^{-1}$

  4. $6.02\times 10^{20}\, mole ^{-1}$

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Correct Option: B

An excess of potassium ions makes KCl crystals appear violet or Lilac in colour since

imperfections in solids solid state the solid state chemistry

  1. some of the anionic sites are occupied by an unpaired electron

  2. some of the anionic sites are occupied by a pair of electrons

  3. there are vacancies at someanionic sites

  4. F-centres are created which impart colour to the crystals

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Correct Option: A,D
Explanation:

When KC1 is heated in vapour of K, some of the Cl leave their lattice site and create anion vacancies. This chloride ion wants to combine with K vapour to form potassium chloride. For doing so K atom loses electrons form K ions. This released electron diffuses into the crystal to get entrapped in the anion vacancy called F-centre. When visible light falls on the crystal, this entrapped electron gains energy, goes to the higher level when it comes back to the ground state, energy is released in the form of light.

If $NaCl$ is doped with $10^{-3}$ mol$\%$ of $SrCl _2$, the concentration of cation vacancies will be: 

$(N _A=6.02\times 10^{23}mol^{-1}$)

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. $6.02\times 10^{18} mol^{-1}$

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

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Correct Option: C
Explanation:

Given that $1$ $mol$ of $NaCl$ is doped with $\cfrac{10^{-3}}{100}$ $mol$ of $Sr^{+2}=10^{-5}$ $mol$


Cation vacancies produced by $Sr^{2+}$ ion $=1$               [$\because$ 1 $Sr^{+2}$ can replace 2 $Na^+$]


So, concentration of cation vacancies produced by $10^{-5}$ mole of $SrCl _2$

$=6.023\times 10^{23}\times 10^{-5}$

$=6.023\times 10^{18}$ per mole

$KBr$ 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

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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. $18$%

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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

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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

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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 .