Tag: the solid state

Questions Related to the solid state

What type of stoichiometric defect is shown by $ZnS$?

imperfections in solids solid state the solid state chemistry

  1. Schottky defect

  2. Frenkel defect

  3. Both Frenkel and Schottky defect

  4. Non-stoichiometric defect

Show answer
Correct Option: B
Explanation:
The defect arises when some of the ions of the lattice occupy interstitial sites leaving lattice sites vacant is known as Frenkel defect. This defect is generally found in ionic crystals where anion is much larger in size than the cation.
The atomic sizes of $Zn$ and $S$ are different. So, we can say that they show Frenkel defect.
So, option $B$ is correct.

Silver halides generally show ?

imperfections in solids solid state the solid state chemistry

  1. Schottky defect

  2. Frenkel defect

  3. both Frenkel and Schottky defects

  4. cation excess defect

Show answer
Correct Option: C
Explanation:

Silver halides show both Frenkel and Schotkky defects. For Frenkel defect the reason is that there is size difference between the sizes of silver and halide.

Schottky defect is possible because silver halides are highly ionic.
So, correct answer is option C.

Assertion: In any ionic solid $[MX]$ with schottky defects, the numbers of positive and negative ions are same.
Reason: Equal number of cation and anion vacancies are present.

imperfections in solids solid state the solid state chemistry

  1. Both assertion and reason are true and reason is the correct explanation of assertion.

  2. Both assertion and reason are true and reason is not the correct explanation of assertion.

  3. Assertion is true but reason is false.

  4. Both assertion and reason are false.

Show answer
Correct Option: A
Explanation:

Schottky Defect: This defect occurs when oppositely charged ions leave their lattice site creating vacancies in such a way that electrical neutrality of crystal is maintained. It is generally seen in highly ionic compounds where a difference in size of cation and anion is small. 

So, an equal number of cations and anions vacancies are present in the crystals with Schottky Defect.

Which of the following defects is also known as dislocation defect?

imperfections in solids solid state the solid state chemistry

  1. Frenkel defect

  2. Schottky defect

  3. Non-stoichimetric

  4. Simple interstitial defect

Show answer
Correct Option: A
Explanation:

Frenkel defect is one in which atom is displaced from its lattice point to the interstitial site, creating a vacancy at the lattice point. Here, since dislocation of atom lattice point happens. So, it is also called as dislocation defect.

Fill in the blanks by choosing an appropriate option. A sample of ferrous oxide has actual formula $Fe {0.93}O _{1.00}.$ In this sample __(i) fraction of metal ions are $Fe^+$ ions. ____(ii) type of non-stoichiometric defect is present in this sample. 

imperfections in solids solid state the solid state chemistry

  1. (i) 0.849 (ii) Metal deficiency

  2. (i) 0.790 (ii) Metal deficiency

  3. (i) 0.145 (ii) Metal excess

  4. (i) 0.93 (ii) Vacancy defect

Show answer
Correct Option: A
Explanation:

Given, sample of ferrous oxide is $Fe _{0.93}O _{1.00}$.

Let number of $Fe^{2+}$ ions is $x$ then number of $Fe^{3+}$ ions is $(0.93-x)$

Now, for electrical neutrality, $(+2)x + (+3)(0.93-x)=+2$

$\Rightarrow 2x+2.79 – 3x = 2$

$\Rightarrow x=0.79$

So, number of $Fe^{2+}$ ions $=0.79$

Number of $Fe^{3+}$ ions $=0.14$

So, fraction of $Fe^{2+}$ ions $= \cfrac {0.79}{0.93}=0.849$

$FeO$ has non stochiometric metal deficiency defect in which number of $Fe^{2+}$ ions are lesser than $O^-$ ions as compared to stochiometric formula. The neutrality is maintained to variable oxidation state possessing capability of $Fe$.

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

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

Show answer
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

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

Show answer
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