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Solid State Test - 32

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Solid State Test - 32
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  • Question 1
    1 / -0
    At zero kelvin, most of the ionic crystals possess :
    Solution

    At zero kelvin, most of the ionic crystals posses no defect. This is due to presence of highly ordered arrangement.

  • Question 2
    1 / -0
    The ABAB packing and ABCABC packing are respectively called as:
    Solution
     
    $$\text { Solution:- Packing of lattice points in a crystal is of 2-types:- } \\$$
    $$\text { 1.) Cubic dose packing (CCP) } \\$$
    $$\text { 2.) hexagonal close packing (HCP) } \\$$
    $$\text { layers of packing sphere or lattice points } \\$$
    $$\text { in ccp & hcp are } 3 \text { . }$$

    $$\text { - CCP is ABCABC ... type } \\$$
    $$\text { and } \\$$
    $$\text { - HCP is } A B \triangle B A B \text { .... type. }$$
     
    $$\text { Examples:- } \\$$
    $$\qquad \text { - Zinc blende }(Z n S)(4: 4)-c c p \text { . } \\$$
    $$\qquad \text { - Wurtzite }(Z n S)(4: 4)-h c p \text { . } \\$$
    $$\text { hence correct option is (A) }$$

  • Question 3
    1 / -0
    Tetragonal crystal system has which of the following unit cell dimensions?
  • Question 4
    1 / -0
    Solid sodium amide, $$NaNH_2$$ has a cubic closed packed arrangement of $$N{ H }_2^-$$ ions with _____ voids occupied by $$Na^+$$ ions.
    Solution
    $$Z_{effective}\quad of\quad {NH_2}^{-}=6\times \cfrac {1}{2}+8\times \cfrac {1}{8}=4$$ (CCP arrangement)

    To maintain the $$NaNH_2$$ formula $$Z_{effective}$$ of $$Na^{+}$$ must be $$4$$.
    So, $$Na^{+}$$ will be present at alternate tetrahedral voids.

    $$Z_{effective}$$ of $$Na^{+}=\cfrac {1}{2}\times 8=4$$

    Answer: (C) half the number of tetrahedral
  • Question 5
    1 / -0
    Which of the following is amorphous?
    Solution
    Amorphous is defined as a substance laking clear structure or shape.
    In quartz glass, elements are not organized in a periodic array, so they don't have a proper shape or structure.

    Hence, quartz glass is am an example of an amorphous solid.
  • Question 6
    1 / -0
    An element (atomic mass $$=100$$ g/mol) having bcc structure has unit cell edge length $$400$$ pm. The density (in g cm$$^{-3}$$) of the element is:
    Solution
    Given, M $$= $$ 100 g/mol, a $$= $$ 400pm 

    For BCC - 

    $$n= 8\times \dfrac{1}{8}+ 1= 2$$

    As we know,

    $$\text{Density}\displaystyle=\frac{n\times M}{a^3\times N_A}$$ $$\displaystyle=\frac{2\times100}{(400\times10^{-10})^3\times6.02\times10^{23}}$$ $$=5.188$$ g cm$$^{-3}$$

    $$(\because 400pm= 400\times 10^{-10} cm)$$

    Hence, the correct option is B.
  • Question 7
    1 / -0
    Average composition of ordinary glass is:
    Solution
    $$Na_2CO_3+xSiO_2\rightarrow Na_2O\cdot xSiO_2+CO_2$$

    $$Na_2SO_4+C\rightarrow Na_2O+CO+SO_2$$

    $$Na_2O+ySiO_2\rightarrow Na_2O\cdot ySiO_2$$

    $$CaCO_3+zSiO_2\rightarrow CaO\cdot zSiO_2+CO_2\uparrow$$

    The overall reaction on simultaneous fusion may be represented as:-
    $$Na_2CO_3+CaCO_3+6SiO_2\rightarrow Na_2O\cdot CaO\cdot 6SiO_2+CO_2\uparrow$$

    Specifically called as soda lime glass composed of approximately $$75$$%
    $$SiO_2$$,$$Na_2O$$ and $$CaO$$ (lime).

    Option A is the answer.
  • Question 8
    1 / -0
    A compound $$AB$$ has a rock type structure with $$A:B =1:1$$. The formula mass of $$AB$$ is $$6.023$$ $$y^{1/3}$$ y amu and the closest $$A-B$$ distance is $$y^{1/3}$$ nm.Calculate the density of lattice.
    Solution
    $$AB$$ has rock-salt $$(A:B: :1:1)$$ structure, i.e., fcc structure $$(n=4)$$ and formula mass of $$AB$$ is 6.023 y g having closest distance $$A-B\:y^{1/3}$$ nm. Therefore, edge length of unit cell
    $$(a)=2(A^++B^-)=2\times y^{1/3}\times10^{-9}m$$

    $$\therefore$$ $$Density of AB=\displaystyle\frac{n\times\:formula\:mass}
    {Av.no.\times V}=\frac{n\times\:formula\:mass}{6.023\times10^{23}\times a^3}$$

    $$=\displaystyle\frac{4\times6.023\times y\times10^{-3}}{6.023\times10^{23}\times(2y1/3\times10^{-9})^3}$$  (formula mass in kg)

    $$=5.0kg/m^3$$ 
  • Question 9
    1 / -0
    Crystal system in which maximum number of Bravais lattices are possible is:
    Solution
    Orthorhombic crystal system has all four lattices i.e. primitive, body-centered, face-centered and end-centered.
  • Question 10
    1 / -0
    The maximum proportion of available volume that can be filled by hard spheres in diamond is:
    Solution
    The maximum packing or the maximum proportion of volume filled by hard spheres in various arrangements are as follows:

    (a) Simple cubic $$\displaystyle=\frac{\pi}{6}=0.52$$

    (b) Body-centered cubic $$\displaystyle=\frac{\pi\sqrt{3}}{8}=0.68$$

    (c) Face-centered cubic $$\displaystyle=\frac{\pi\sqrt{2}}{6}=0.74$$

    (d) Hexagonal closed packing $$\displaystyle=\frac{\pi\sqrt{2}}{6}=0.74$$

    (e) Diamond $$\displaystyle=\frac{\pi\sqrt{3}}{6}=0.34$$
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