Schottky Defect

Q. An element (atomic mass $=50\text{g/mol}$) that has a fcc structure has a unit cell edge length of $200\text{pm}$. The density of the element is:
(Take $N_A=6\times {10}^{23}$)

1. $10{\text{g cm}}^{-3}$
2. $15.67{\text{g cm}}^{-3}$
3. $17.42{\text{g cm}}^{-3}$
4. $41.66{\text{g cm}}^{-3}$

Q.

What is the color of Zinc metal?

1. reddish-brown

2. silvery

3. white

4. grey

Q.

A crystal is made of particles X, Y and Z. X forms FCC packing, Y occupies all octahedral voids of X and Z occupies all tetrahedral voids of X. If all the particles along one body diagonal are removed, then the formula of crystal would be

1. $XY{Z}_2$

2. $X_8{Y}_4{Z}_5$

3. $X_{2}Y{Z}_2$

4. $X_5{Y}_4{Z}_8$

Q. Total volume of atoms present in a face centred cubic unit cell of a metal is ($r$ is atomic radius):

1. $\frac{20}{3}\pi r^3$
   
2. $\frac{24}{3}\pi r^3$
   
3. $\frac{12}{3}\pi r^3$
   
4. $\frac{16}{3}\pi r^3$
   

Q.

Frenkel defects are not found in alkali metals halides reason out

Q. In a cubic lattice of X and Y, X atoms are present at the corners and body centre while Y atoms are at face centres and edge centres. What would be the simplest formula of the compound be if two corner atoms of X and 4 edge centre atoms of Y are replaced by Z atoms?

1. $X_7{Y}_{19}{Z}_3$
2. $X_3{Y}_{19}{Z}_7$
3. $X_{20}{Y}_5{Z}_7$
4. $X_7{Y}_{20}{Z}_5$

Q. An element (at. Wt. = 50) crystallises in FCC lattice, with a = 0.50 nm. What is the density of the unit cell if it contains 0.25% Schottky defects? $(use{N}_A=6\times {10}^{23})$ (a = Edge length of the unit cell)

1. $2.66\text{g/cc}$
2. $3.06\text{g/cc}$
3. $2.0\text{g/cc}$
4. None of these

Q.

Which of the following defects decrase the density ?

(a) Interstitial defect (b) Vacancy defect

(c) Frenkel defect(d) Schottky defect

Q. Platinum crystallizes in a face – centered cubic crystal with a unit cell of edge length 'a'. The distance between nearest neighbour is:

1. $a$
2. $a\frac{\sqrt{3}}{2}$
3. $a\frac{\sqrt{2}}{2}$
4. $a\frac{\sqrt{2}}{4}$

Q. Why does AgBr shows schottky as well as interstitial defect ??

Q. An element crystallises in face-centred cubic lattice with density as $5g/c{m}^3$ and edge length of the side of unit cell is 400 pm.
Take $N_A=6\times {10}^{23}$ Then the molar mass of the element in $gmo{l}^{-1}$ is :

Q. IN A BCC UNIT CELL OF COMPUND AB, A IS LOCATED AT CUBICAL VOID .CALCULATE THE RATIO OF 4TH C.N AND 3RDC.N OF A

Q. The number of atoms in $50g$ of a fcc crystal with density, $\rho =10gc{m}^{-3}$ and cell edge, $a=200pm$ are

1. $0.5\times {10}^{25}$
2. $25\times {10}^{23}$
3. $1.0\times {10}^{25}$
4. $2.0\times {10}^{25}$

Q. A metal 'X' forms a body centred cubic lattice whose unit cell edge length is $300\text{pm}$. Calculate the density of 'X'.
Given: $\text{Molar mass of metal 'X'}=78{\text{g mol}}^{-1}$

1. $9.6gc{m}^3$
2. $10.49gc{m}^3$
3. $104.9gc{m}^3$
4. $8.45gc{m}^3$

Q. Aluminium crystallizes in an FCC structure. Atomic radius of the metal is 125 pm. What is the length of the side of the unit cell of the metal?

Q. Which of the following compounds exhibits Schottky defect?

1. $Ca{F}_2$
2. $AgI$
3. $CsCl$
4. $ZnS$

Q. A metal crystallizes in fcc structure with a unit cell side of $500\text{pm}$. If the density of the crystal is $1.33\text{g/cc}$, the molar mass of the metal is close to?

1. $23$
2. $24$
3. $25$
4. $26$

Q.

Schottky defect is observed in crystals when .....................

(a) some cations move from their lattice site to interstitial sites

(b) equal number of cation and anions are missing from the lattice

(c) some lattice sites are occupied by electrons

(d) some impurity is present in the lattice

Q. A copper complex crystallising in a CCP lattice with a cell edge of $0.4518nm$ has been revealed by employing X-ray diffraction studies. The density of a copper complex is found to be $7.62gc{m}^{-3}.$
The molar mass of copper complex is __________
$gmo{l}^{-1}.$ (Nearest integer) [Given : $N_A=6.022\times {10}^{23}mo{l}^{-1}]$

Q. The density and edge length values for a crystalline element with fcc lattice are 10 g $c{m}^{-3}$ and 400 pm respectively. The number of unit cells in 32 g of this crystal is

1. $8\times {10}^{23}$
2. $5\times {10}^{22}$
3. $8\times {10}^{22}$
4. $5\times {10}^{23}$

Q. If an hypothetical metal crystallises in a face centered cubic unit cell having density $\left(d\right)=100{\text{g/cm}}^3$ and edge length of the unit cell is $100\text{pm}$, then, what is the molar mass of the metal:
[1 Mark]

1. $15.05\text{g/mol}$
2. $10.02\text{g/mol}$
3. $16.90\text{g/mol}$
4. $9.06\text{g/mol}$

Q. An element crystallizes in a structure having fcc unit cell of an edge length of $200pm$. Calculate the density (in $gc{m}^{-3}$), if $200g$ of this element contains $24\times {10}^{23}$ atoms.

1. 41.6
2. 83.3
3. 119.4
4. 28.9

Q. Which of the following statement regarding crystal defects is /are not correct?

1. Schottky defects are dislocation defects
2. Three cationic vacancies are created per ion of $A{l}^{3+}$ inserted if NaCl crystals are doped with $A{l}^{3+}$ ion
3. Addition of $As$ to $Si$ results in formation of n-type semiconductors
4. Packing fraction remains unaffected in vacancy defect

Q.

Give reasons :A) Frenkel defects are not found in alkly metal halides.

B) schottky deffect lower the density of related solides

Q.

In Schottky defect:

1. a lattice site is occupied by electron.

2. an ion occupies interstitial position between lattice points.

3. the density of solid increases.

4. equal number of cations and anions are missing from the lattice sites.

Q. potassium iodide has cubic unit cell with edge length 705pm the density of ki is 3.12g/cm^3 how many k+ and I- ions are contained in the unit cell

Q. In Schottky defect, number of missing anions and cations in ionic solids are same.

1. True
2. False

Q.

Assertion: Schottky defect doesn’t have any effect on density of crystal.

Reason: Equal no. of cations and anions missing from the Lattice Points.

1. 1 is correct, 2 is correct and 2 is correct explanation of 1

2. 1 is correct, 2 is correct and 2 is not correct explanation of 1

3. 1 is correct, 2 is wrong

4. 1 is wrong, 2 is correct

Q. how to find the number of octahedral voids in nacl crystal and zns crystal?

Q.

The correct statement in the following is

[MP PET 1997]

1. In ionic compounds having Frenkel defect the ratiois high

2. The coordination number of Na⁺ ion in NaCl is 4

3. The ionic crystal of AgBr has Schottky defect

4. The unit cell having crystal parameters, a=b≠c, α=β=90°, γ=120°