12th Class Chemistry The Solid State / ठोस प्रावस्था Question Bank

done Case Based (MCQs) - Solid State Total Questions - 19

• question_answer1)

  Direction (1 - 5): Read the given passages and answer the questions that follow.

  There are certain substances that are neither good conductors (metals) nor insulators (glass). A substance which has crystalline structure and contains very few electrons at room temperature is called semiconductor. At room temperature, it behaves like an insulator. Its resistivity lies between that of conductor and insulator. If suitable impurities are added to the semiconductor, controlled conductivity can be provided. Some examples of semiconductors are silicon, germanium etc.

  Current conduction in a semiconductor occurs through the movement of free electrons and holes collectively known as charge carriers. Adding impurity atoms to a semiconducting material, known as 'doping', greatly increases the number of charge carriers within it. When a doped semiconductor contains mostly free holes it is called "p-type" and when it contains mostly free electrons it is known as "n-type".

  (Reference: Md. F. Rahman (2014). A Review on Semiconductors Including Applications and Temperature Effects in Semiconductors. American Scientific Research Journal for Engineering, Technology, and Sciences, Vol 7, No. 1, pp 50-70)

  Silicon doped with electron-rich impurity forms:
  A)
  p-type semiconductor done clear
  B)
  n-type semiconductor done clear
  C)
  intrinsic semiconductor done clear
  D)
  insulator done clear
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• question_answer2)
  Which of the following represents correct order of conductivity in solids ?
  A)
  \[{{K}_{metals}}>>{{K}_{insulators}}<{{K}_{semiconductors}}\] done clear
  B)
  \[{{K}_{metals}}<<{{K}_{insulators}}<{{K}_{semiconductors}}\] done clear
  C)
  \[{{K}_{metals}}={{K}_{semiconductors}}<{{K}_{insulators}}=zero\] done clear
  D)
  \[{{K}_{metals}}<{{K}_{insulators}}<{{K}_{semiconductors}}\ne zero\] done clear
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• question_answer3)
  Which of the following is true about the charge acquired by p-type semiconductors?
  A)
  positive done clear
  B)
  neutral done clear
  C)
  negative done clear
  D)
  depends on concentration of p-type impurity done clear
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• question_answer4)

  Q.4 and Q.5 are assertion-reason type. Choose the correct answer out of the following choices:

  Assertion: Semi-conductors are solids with conductivities in the intermediate range from \[{{10}^{-6}}-{{10}^{4}}\,oh{{m}^{-1}}\,m\]

  Reason: Intermediate conductivity in semiconductor is due to partially filled valence band.

   
  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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• question_answer5)

  Assertion: Silicon doped with boron form n-type semiconductor.

  Reason: Boron in silicon behaves as an electron deficient impurity.

   
  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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• question_answer6)

  Direction (6 - 9): Point defects are the irregularities from ideal arrangement around a point or an atom in a crystalline substance. In ionic solids. Frenkel defect is shown when the smaller ion is dislocated from its normal site while Schottky defect is basically a vacancy defect. (Source N.C.E.R.T. Book)

  The defect shown by ionic compounds as in fig. 'a' and 'b' are called respectively as
  A)
  Schottky, Frenkel done clear
  B)
  Frenkel, Schottky done clear
  C)
  Electronic defects, F-centre done clear
  D)
  None of these. done clear
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• question_answer7)
  What is the effect of these defects on the density of the solid?
  A)
  Increases, increases done clear
  B)
  Decreases, decreases done clear
  C)
  No change, decreases done clear
  D)
  Decreases, no change. done clear
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• question_answer8)
  Which ionic compound can show defect shown in Fig. 'b'.
  A)
  ZnS                               done clear
  B)
  AgCl done clear
  C)
  NaCI                             done clear
  D)
  None of these. done clear
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• question_answer9)
  Which of the following defects is also known as dislocation defect?
  A)
  Frenkel defect done clear
  B)
  Schottky defect done clear
  C)
  Non-stoichiometric defect done clear
  D)
  Simple interstitial defect. done clear
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• question_answer10)

  Direction (10 - 14): No crystal is found to be perfect at room temperature. The defects present in the crystals can be stoichiometric or non-stoichiometric. Due to non-stoichiometric defects, the formula of the ionic compound is different from the ideal formula. For example, the ideal formula of ferrous oxide should be FeO but actually in one sample, it was found to be \[F{{e}_{0.93}}O\]. This is because the crystal may have some ferric ions in place of frrous ions. These defects change the properties of the crystals. In some cases, defects are introduced to have crystals of desired properties as required in the field of electronics. Doping of elements of group 14 with those of group 13 or 15 is most common. In ionic compounds, usually the impurities are introduced in which the cation has higher valency than the cation of the parent cyrstal e.g., \[SrC{{l}_{2}}\] into NaCI.

  Which of the following dopings will produce p-type semiconductor?
  A)
  Silicon doped with arsenic done clear
  B)
  Germanium doped with phosphorus done clear
  C)
  Germanium doped with aluminium done clear
  D)
  Silicon doped with phosphorus. done clear
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• question_answer11)
  Zinc oxide (ZnO) is white when cold and yelllow when hot. It is due to the development of :
  A)
  Frenkel defect     done clear
  B)
  Schottky defect done clear
  C)
  Metal excess defect done clear
  D)
  Metal deficiency defect. done clear
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• question_answer12)
  NaCI was doped with \[{{10}^{-3}}\] mol % \[SrC{{l}_{2}}\]. The concentration of the cation vacancies is
  A)
  \[6.02\times {{10}^{18}}\text{ }mo{{l}^{-1}}\] done clear
  B)
  \[6.02\times {{10}^{15}}\text{ }mo{{l}^{-1}}\] done clear
  C)
  \[6.02\times {{10}^{21}}\text{ }mo{{l}^{-1}}\] done clear
  D)
  \[6.02\times {{10}^{12}}\text{ }mo{{l}^{-1}}\] done clear
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• question_answer13)
  A metal oxide has empirical formula \[{{M}_{0.96}}{{O}_{1.00}}\]. What will be the precentage of \[{{M}^{2+}}\] ions in the crystal?
  A)
  \[90\centerdot 67\] done clear
  B)
  \[91\centerdot 67\] done clear
  C)
  \[8\centerdot 33\] done clear
  D)
  \[9\centerdot 33\] done clear
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• question_answer14)
  Which type of 'defect' has the presence of cations in the interstitial sites?
  A)
  Schottky defect               done clear
  B)
  Frenkel defect done clear
  C)
  Vacancy defect   done clear
  D)
  Metal deficiency defect done clear
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• question_answer15)

  Direction (15 - 19): A student of class XII studied the close packing of spheres, with vacant sites (or voids) known as holes. These are of two types i. e. tetrahedral and octahedral voids. A tetrahedral void is formed when four spheres placed at the corners of a tetrahedron touch each other. An octahedral void is created, when three spheres arranged in the corners of an equilateral triangle are placed over another similar set of three spheres pointing in the opposite direction. The actual size of these voids is linked to that of the spheres i.e. greater the size of the spheres, more will be the size of the voids.

  In the following questions, a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices :

  Assertion: Hexagonal close packing is more tight than cubic close packing.

  Reason: Co-ordination number in both the cases is 12.

  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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• question_answer16)

  Assertion: In a close packing of spheres, a tetrahedral hole is surrounded by four spheres whereas an octahedral hole is surrounded by six spheres.

  Reason: A tetrahedral void has a tetrahedral shape while an octahedral void has an octahedral shape.

  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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• question_answer17)

  Assertion: In NaCI crystal, each \[N{{a}^{+}}\] ion is touching six \[C{{l}^{-}}\] ions but these \[C{{l}^{-}}\] ions donot touch each other.

  Reason: The ratius ration \[{{r}_{Na}}+/{{r}_{C{{l}^{-}}}}\] is greater than 0.414 required for exact fitting.

  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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• question_answer18)

  Assertion: In NaCI structure, \[N{{a}^{+}}\] ions occupy octahedral holes and \[C{{l}^{-}}\] ions occupy c.c.p.

  Reason: The distance of the nearest neighbours in NaCI structure is all, where a/2, is the edge length of the cube.

  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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• question_answer19)

  Assertion: The number of tetrahedral voids is double the number of octahedral voids,

  Reason: The size of the tetrahedral voids is half than that of the octahedral voids.

  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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