Tag: the solid state

Quizzes (4) Questions (85)

Questions Related to the solid state

Multiple choice imperfections in solids solid state the solid state chemistry

Which kind of defect is shown by the given crystal?
${ K }^{ + }$  ${ Cl }^{ - }$   ${ K }^{ + }$   ${ Cl }^{ - }$   ${ K }^{ + }$     ${ Cl }^{ - }$
${ Cl }^{ - }$  $\Box $      ${ Cl }^{ - }$    ${ K }^{ + }$   $\Box $       ${ K }^{ + }$
${ K }^{ + }$   ${ Cl }^{ - }$   $\Box $     ${ Cl }^{ - }$     ${ K }^{ + }$    ${ Cl }^{ - }$ 
${ Cl }^{ - }$   ${ K }^{ + }$   ${ Cl }^{ - }$   ${ K }^{ + }$   $\Box $        ${ K }^{ + }$   

  1. Schottky defect

  2. Frenkel defect

  3. Schottky Frenkel defects

  4. Substitution disorder
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the given crystal equal number of cations and anions are missing (two ${K}^{+}$ and two ${Cl}^{-}$) from their normal lattice sites and the crystal maintains electrical neutrality. Hence, this is Schottky defect.

Multiple choice imperfections in solids solid state the solid state chemistry

The appearance of colour in solid alkali metal halides is generally due to: 

  1. schottky defect

  2. frenkel defect

  3. interstitial position

  4. F-centre
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In F-centre defect in which an anionic vacancy in a crystal is filled by one or more unpaired electron. These electron absorb light in the visible region and emits colour. So, appearance of colour in solid alkali metal halides is generally due to F-centre.

Multiple choice imperfections in solids solid state the solid state chemistry

Select the incorrect statement :

  1. Stoichiometry of crystal remains unaffected due to Schottky defect

  2. Frenkel defect usually shown by ionic compounds having low coordination number

  3. F-centres generation is responsible factor for imparting the colour to the crystal

  4. Density of crystal always increases due to substitutional impurity defect
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

(4) Density of crystal not $\uparrow$ es always it may remain constant sometimes.

Multiple choice imperfections in solids solid state the solid state chemistry

Which of the following defect is seen in $FeO$? 

  1. Metal excess defect

  2. Metal deficiency defect

  3. Displacement defect

  4. Impurity defect
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$FeO$ has metal deficiency defect. Metal deficiency defect is supposed to arise when there are lesser number of positive ions than negative ions. In case of $FeO$, the positive ions are missing from their lattice sites. 

The additional negative charge is balanced by some nearby metal ion by acquiring one more positive charge. It happens in $FeO$ because $Fe$ has capacity of showing variable oxidation states.

Multiple choice imperfections in solids solid state the solid state chemistry

In a crystal, at $827^{\circ}C$, one out of $10^{10}$ lattice site is found to be vacant, while in the same solid, one out of $2 \times 10^9$ lattice site is found to be vacant at $927^{\circ}C$. What is the enthalpy of vacancy formation in kJ/mol unit?

  1. $76.8$
  2. $176.8$
  3. $33$
  4. $23$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$\cfrac {^nV}{N}=Ae^{-\Delta H _V/RT} \longrightarrow (x)$

$\left(\cfrac {^nV}{N}\right) _{827^oC}=\cfrac {1}{10^{10}} \longrightarrow (1)$
$\left(\cfrac {^nV}{N}\right) _{927^oC}= \cfrac {1}{2 \times 10^9} \longrightarrow (2)$                                   $\therefore T _1= 827+273=1100K ; T _2=927+273=1200K$

$\Rightarrow \cfrac {(2)}{(1)}= \cfrac {1/2\times 10^9}{1/10^{10}}= \cfrac {10^ {10}}{2 \times 10^9}= 0.5 \times 10=5$
$x \Rightarrow 2.303 \log 5= - \cfrac {\Delta H _V}{R} \left(\cfrac {1}{T _1}-\cfrac {1}{T _2}\right)$
$\therefore \Delta H _V= 2.303 \times \log 5 \times 8.314 \times \left(\cfrac {1100\times 1200}{100}\right)$
               $=1.766 \times 10^5 J$
               $=176.6kJ/mol$ $unit$ .

Multiple choice imperfections in solids solid state the solid state chemistry

Calcium crystallizes in a face centred cubic unit cell with a $=0.556$ nm. Calculate the density if it contains:

(i) $0.1\%$ Frenkel defect
(ii) $0.1\%$ Schottky defect

  1. $1.546, 1.546$
  2. $1.546, 1.544$
  3. $15.46, 15.46$
  4. $21.76, 41.66$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$1.$ In frenkel defect there is no change in original density

$\rho=\cfrac{Z\times M _A}{N _A\times a^3}$
$\implies \rho=\cfrac{4\times 40}{6.023\times 10^{23}\times 171.8\times 10^{-24}}$
$\implies \rho=1.546$ $g/cm^3$

$2.$ In schottky defect $Z _{eff}$ changes so density changes
$Z _{new}=4-\cfrac{4\times 0.1}{100}=3.996$
$\rho =\cfrac { Z\times M _{ A } }{ N _{ A }\times a^{ 3 } } $
$\implies \rho =\cfrac { 3.996\times 40 }{ 6.023\times 10^{ 23 }\times 171.8\times 10^{ -24 } } $
$\implies \rho =1.544$$g/cm^{ 3 }$

Multiple choice imperfections in solids solid state the solid state chemistry

Statement 1: KCl is more likely to show schottky defect while Lil is more likely to show Frenkel defect.
Statement 2: Schottky defect is more likely in ionic solids in which cations and anions are of comparable size while Frenkel defect is more likely is which cations and anions have large differences in their ionic sizes.

  1. Statement-1 is true, Statement-2 is true and Statement-2 is correct explanation for Statement-1

  2. Statement-1 is true, Statement-2 is true and Statement-2 is not the correct explanation for Statement-1

  3. Statement-1 is true but Statement-2 is false

  4. Statement-1 is false but Statement-2 is true
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In case of KCl, the cation and the anion are of comparable size while in case of LiI, the cation Li+ is very small as compared to the iodide ion, I-. Hence, KCl is more likely to show Schottky defect while LiI tends to show Frenkel defect. Thus, the statements 1 and 2 are true and 2 is correct explanation of 1.

Multiple choice imperfections in solids solid state the solid state chemistry

Statement-I:  Solids having more $F-$centres possess intense colours.

Statement-II:  Excess of $Na^{+}$ in $NaCl$ solid having F-centres makes it appear to pink.

  1. Statement-I is correct but Statement-II is wrong

  2. Statement-I is wrong but Statement-II is correct

  3. Both Statement-I and Statement-II are correct and Statement-II is correct explanation of Statement-I

  4. Both Statement-I and Statement-II are correct but Statement-II is not correct explanation of Statement-I
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

F-centres are indeed responsible for the intense colors in alkali halides due to the excitation of trapped electrons. However, the color of NaCl with F-centres is yellow, not pink, making statement II incorrect.

Multiple choice imperfections in solids solid state the solid state chemistry

Which of the following statements are correct?

  1. Dislocation of ion from lattice site to interstitial site is called Frenkel defect.

  2. Missing of +ve and -ve ions from their respective position producing a pair of holes is called Schottky defect.

  3. The presence of ions in the vacant interstital sites along with lattice point is called interstital defect.
  4. Non-stoichiometric $NaCl$ is yellow solid.
Reveal answer Fill a bubble to check yourself
A,B,C,D Correct answer
Explanation

Frenkel defect: This type of defect is created when an ion leaves its appropriate site in the lattice and occupies an interstitial site. A hole or vacancy is thus produced in the lattice.

Schottky defect: This type of defect is produced when one cation and anion are missing from their respective positions leaving behind a pair of holes.

The presence of ions in the vacant interstital sites along with lattice point is called interstital defect.

 When alkali metal halides are heated in an atmosphere of vapours of the alkali metal, anion vacancies are created. 


The anions (halide ions) diffuse to the surface of the crystal from their appropriate lattice sites to combine with the newly generated metal cations. The electron lost by the metal atom diffuse through the crystal is known as F-centres. 


The main consequence of metal excess defect in the development of colour in the crystal. For example, when $NaCl$ crystal is heated in an atmosphere of $Na$ vapours, it becomes yellow.


Therefore, all statements are correct.