Tag: the solid state

Questions Related to the solid state

The correct statement(s) regarding defects in solid is (are)

imperfections in solids solid state the solid state chemistry

  1. Frenkel defect usually favoured by a very small difference in the sizes of cation and anion

  2. Frenkel defect is a dislocation defect

  3. Trapping of an electron in the lattice leads to the formation of F-centre

  4. Schottky defect have no effect on the physical properties of solids

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Correct Option: B,C

Missing of one cation and one anion from the crystal lattice is called

imperfections in solids solid state the solid state chemistry

  1. ionic defect

  2. crystal defect

  3. schottky defect

  4. frenkel defect

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Correct Option: C
Explanation:

Schottky defect arises due to a vacancies at cation sites and equal number of vacancies at anion sites.

Hence, option C is correct.

In a crystal, pair of ions are missing from normal sites. This is an example of which defect?

imperfections in solids solid state the solid state chemistry

  1. Extended defect

  2. Interstitial defect

  3. Frenkel defect

  4. Schottky defect

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Correct Option: D
Explanation:

Schottky defect arises due to a vacancies at cation sites and equal number of vacancies at anion sites.

Which of the following crystals does not exhibit Frenkel defect?       

imperfections in solids solid state the solid state chemistry

  1. $AgBr$

  2. $AgCl$

  3. $KBr$

  4. $ZnS$

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Correct Option: C
Explanation:

Condition for Frankel defects in an ionic crystal is-

  1. The size difference between the ions should be large.
  2. Smaller ion (cation) move to interstitial site.

Frenkel defect generally appears in ZnS, AgBr, AgI, AgCl etc.
Alkali metal shows Schottky defect. Here KBr exhibits Schottky defect. However, it does not show Frankel defect. ZnS has a large size difference between the ions.

Option C is correct.

The correct statement(s) regarding defects in solids is(are):

imperfections in solids solid state the solid state chemistry

  1. Frenkel defect is usually favoured by a very small difference in the sizes of cation and anion.

  2. Frenkel defect is a dislocation defect.

  3. Trapping of an electron in the lattice leads to the formation of F-center

  4. Schottky defects have no effect on the physical properties of solids.

Show answer
Correct Option: B,C
Explanation:

Frenkel defect is a defect which 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.
Frenkel defect is exhibited in ionic compounds in which the radius ratio is low. The cations and anions differ much in their sizes and the ions have low co-ordination numbers. Examples are ZnS, AgBr, AgI, AgCl.
The Schottky defect is a defect which is produced when one cation and anion are missing from their respective positions leaving behind a pair of holes. The crystal as a whole remains neutral because the number of missing positive ions (cations) and negative ions (anions) is the same.

Consequences of Schottky defect:
1. The density of the crystal decreases.
2. The crystal begins to conduct electricity to a small extent by the ionic mechanism.
3. The presence of too many voids lowers lattice energy or the stability of the crystal.
4. F-center: A colour centre consisting of an electron trapped by a negative ion vacancy in an ionic crystal such as an alkali halide or an alkaline-earth fluoride or oxide.

Hence, the correct options are $\text{B}$ and $\text{C}$.

Scotty defect is observed in____________.

imperfections in solids solid state the solid state chemistry

  1. $NaCl$

  2. $KCl$

  3. $CsCl$

  4. $BaCl _2$

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Correct Option: A,B,C
Explanation:

Schottky defect is the defect which is produced when one cation and anion are missing from their respective positions leaving behind a pair of holes. The crystal as a whole remains neutral because the number of missing positive ions (cations) and negative ions (anions) is the same.
For Schottky defect, co-ordination numbers of the ions should be high., Examples of ionic solids showing this defect are NaCl, CsCl, KCI, KBr etc.
Consequences of Schottky defect are as follows:
1. Density of the crystal decreases.
2. The crystal begins to conduct electricity to small extent by ionic mechanism.
3. The presence of too many voids lowers lattice energy or the stability of the crystal.

Statement: The imperfectness in crystal increases with increase in temperature.

State whether the given statement is true or false
imperfections in solids solid state the solid state chemistry

  1. True

  2. False

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Correct Option: A
Explanation:
The imperfectness in crystal increases with increase in temperature. Hence, these imperfections are called thermodynamic defects. When the temperature is high, imperfections are high and when the temperature is low, imperfections are low.
Statement: Imperfection in solids give rise to new properties in it.

State whether the given statement is true or false
imperfections in solids solid state the solid state chemistry

  1. True

  2. False

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Correct Option: A
Explanation:
Imperfection in solids changes the properties of crystals and gives rise to new properties in it. These include electrical and thermal conductivity and density.

Non-stoichiometric compounds is/are :

imperfections in solids solid state the solid state chemistry

  1. $Cu _2O$

  2. $Cu _2S$

  3. FeO

  4. $Hg _2Ba _2YCaCu _2O _ 7$

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Correct Option: A,B,C,D
Explanation:
Non-stoichiometric compounds are chemical compounds with an elemental composition that cannot be represented by usual integral numbers. They are almost always inorganic compounds and almost invariably solids. In such materials, some small percentage of atoms are missing or too many atoms are packed into an otherwise perfect lattice work. They exhibit special electrical or chemical properties because of these flaws or defects. For example, when atoms are missing, the other atoms can move through the solid more rapidly. Non-stoichiometry is represented by many metal oxides and sulfides. For example, stoichiometric iron(II) oxide, which is rare, has the formula FeO whereas the more common nonstoichiometric material has the formula $Fe _{0.95}O$. Non-stoichiometric compounds are homogeneous, they are not mixtures. Batteries often rely on materials that can exist in a range of non-stoichiometric states.
Therefore, all given compounds are non-stoichiometric.

Assertion: Frenkel defects are shown by $AgX$.
Reason: $Ag^+$ ions have small size.

imperfections in solids solid state the solid state chemistry

  1. Both Assertion and Reason are correct and Reason is the correct explanation of Assertion

  2. Both Assertion and Reason are correct but Reason is not the correct explanation of Assertion

  3. Assertion is correct but Reason is not correct

  4. Assertion is not correct but Reason is correct

  5. Both Assertion and Reason are not correct

Show answer
Correct Option: A
Explanation:

Frenkel defect is the defect which 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.
Frenkel defect is exhibited in ionic compounds in which the radius ratio is low. The cations and anions differ much in their sizes and the ions have low co-ordination numbers. Examples are $ZnS, AgBr, AgI, AgCl$.