Tag: solid state

Questions Related to solid state

A semiconductor of Ge can be made p-type by adding which impurity?

chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

  1. trivalent impurity

  2. tetravalent impurity

  3. pentavalent impurity

  4. hexavalent impurity

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Correct Option: A
Explanation:

A semiconductor of Ge can be made p-type by adding trivalent impurity and for n-type SC pentavalent impurity is dopped.

Assertion (A): Group-$13$ doped crystals of silicon are called a p-type semiconductors.
Reason (R): Holes (positive in charge) appear to be responsible for the semiconducting properties.
chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

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

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

  3. Assertion is true but Reason is false.

  4. Assertion is false but Reason is true

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Correct Option: A

Which of the following statement is correct?

chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

  1. Silicon doped with Boron is a n-type semi conductor.

  2. Silicon doped with Arsenic is a p-type semiconductor.

  3. Semiconductors are good conductors of electricity.

  4. Electrical conductivity of semiconductors increases with increasing temperature.

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Correct Option: D
Explanation:
The electrical conductivity of a semiconductor increases exponentially with an increase in temperature because as temperature is increased, more electrons get energy and can jump to the conduction band which increases conductivity.
$\sigma=Ce^{\displaystyle {-E _g} /{2KT}}$

Assertion: Group-$15$ doped crystals of silicon are called an n-type semiconductor.


Reason: Neutrons are responsible for the semiconducting properties.

chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

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

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

  3. The Assertion is true but Reason is false

  4. The Assertion is false but Reason is true

Show answer
Correct Option: C
Explanation:

Group-15 doped crystals of silicon are called a n-type semiconductors because of the presence of a valence electron and electrons are responsible for the semiconducting properties.

The density for simple cubic lattice is :


[where A is atomic weight, N is the Avogadro number and a is lattice parameter]

chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

  1. $\displaystyle \frac{4A}{Na^3}$

  2. $\displaystyle \frac{2A}{Na^3}$

  3. $\displaystyle \frac{A}{Na^3}$

  4. $\displaystyle \frac{A}{Na^2}$

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Correct Option: C
Explanation:

Density = $\displaystyle \frac{\text{Mass of atom in unit cell}}{{\text{Total volume of unit cell}}} = \cfrac{nM}{V _cN _A} $


For simple cubic lattice, 

$n = 1  \\   V _c = a^3  \\$

$Given,  M = A$

$= \cfrac{A}{Na^3}$

Statement: The melting point of ice changes markedly with pressure.

State whether the given statement is true or false.
chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

  1. True

  2. False

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Correct Option: A
Explanation:

The melting point of ice is $0^oC$ $(32\ F,\ 273.15\ K)$ at standard pressure. A significant increase of pressure is required to lower the melting point of ordinary ice. The pressure exerted by an ice skater on the ice only reduces the melting point by approximately $0.09^oC$ $(0.16\ F)$.

Glass is an example of _____ solids.

chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

  1. amorphous

  2. shaped

  3. structured 

  4. determinate

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Correct Option: A
Explanation:

Glass is a non-crystalline, often transparent amorphous solid, that has widespread practical, technological, and decorative uses in, for example, window panes, tableware, optics, and optoelectronics.


Hence, the correct option is $\text{A}$

Statement: In an insulator, the band gap is small.

State whether the given statement is true or false.
chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

In an insulator, the bandgap is large. More energy is required to promote electrons from valence band to conduction band. This energy is not available. The electrons remain in the valence band and cannot move freely. Hence, insulators are bad conductors of heat and electricity.


Hence, the given statement is $\text{false}$

Frenkel defect is observed in:

chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

  1. $MgCl _2$

  2. $AgCl$

  3. $ZnS$

  4. $AgI$

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Correct Option: B,C,D
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.

Assertion: The electrical conductivity of a semiconductor increases with increase in temperature.
Reason: With increase in temperature, large number of electrons from the valence band can jump to the conduction band.
chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

  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 incorrect

  4. Assertion is incorrect but Reason is correct

  5. Both Assertion and Reason are incorrect

Show answer
Correct Option: A
Explanation:
As temperature increases, some electrons are thermally released from the covalent bonds in pure Si or Ge. 
These electrons are free to move in the crystal and are responsible for electrical conductivity.
With an increase in temperature, the number of electrons released increases and the electrical conductivity increases.
This type of conduction is called intrinsic conduction.
Hence, both Assertion and Reason are correct and Reason is the correct explanation of Assertion.