Voids

Q.

An element crystallises in a face-centred cubic ($\mathrm{fcc}$) unit cell with a cell edge $\mathrm{a}$. The distance between the centres of the two nearest octahedral voids in the crystal lattice is:

1. $\mathrm{a}$

2. $\frac{a}{2}$

3. $\sqrt{2a}$

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

Q. Element A has a face centred unit cell in which A is absent from half of the face centres. The packing fraction is $\frac{x\times \sqrt{2}\pi }{96}$.
The value of x is :

Q. 8.In a cubic unit cell atoms A are present at all corners, atoms B at alternate face centres and atoms C at alternate edge centres of cube. Hence formula of compound is

Q. 19. relation ship between radius of tetrahedral void and radius of atom in closed packing

Q.

For IUPAC nomenclature of elements with atomic number greater than 100, the abbreviation used for digit zero is:

1. MN

2. n

3. o

4. N

Q. 39 What is tetrahedral voids and octahedral voids?

Q. 35. Minimum distance between two tetrahedral voids if a is the edge length of the cube is (1) a/4 (2) a/2root2 (3) a/2 (4) root3a/4

Q. A solid element exists in simple cubic crystal. If its atomic radius is $1.0\stackrel{o}{A}$ and the ratio of packing fraction to density is $0.1c{m}^3/g,$ then the atomic mass of the element is $(N_A\approx 6\times {10}^{23})$

1. $8\pi$
2. $16\pi$
3. $4\pi$
4. $6\pi$

Q. Atoms of element B form HCP lattice and those of element A occupy two thirds of tetrahedral voids. The formula of the compound is .

1. $A_4{B}_3$
2. $A_4{B}_6$
3. $A_8{B}_3$

Q. 13. Distance between two tetrahedral voids and between two octahedral voids?

Q. 50 What are the position of tetrahedral voids?

Q. The fraction of total volume occupied by the atoms present in a simple cube is :
AIPMT -2007

1. $\frac{\pi }{6}$
2. $\frac{\pi }{4}$
3. $\frac{\pi }{3\sqrt{2}}$
4. $\frac{\pi }{4\sqrt{2}}$

Q. If the radius of a metal atom is $2.00\stackrel{\circ }{A}$ and its crystal structure is fcc lattice, what is the volume (in $c{m}^3$) of one unit cell?

1. $8.00\times {10}^{-24}$
2. $4.45\times {10}^{-23}$
3. $1.81\times {10}^{-22}$
4. $0.5\times {10}^{-23}$

Q. A solid element exists in simple cubic crystal. If its atomic radius is $1.0\stackrel{o}{A}$ and the ratio of packing fraction to density is $0.1c{m}^3/g,$ then the atomic mass of the element is $(N_A\approx 6\times {10}^{23})$

1. $4\pi$
2. $6\pi$
3. $16\pi$
4. $8\pi$

Q. If the radius of a metal atom is $2.00\stackrel{\circ }{A}$ and its crystal structure is fcc lattice, what is the volume (in $c{m}^3$) of one unit cell?

1. $0.5\times {10}^{-23}$
2. $1.81\times {10}^{-22}$
3. $8.00\times {10}^{-24}$
4. $4.45\times {10}^{-23}$

Q. An atom crystallizes in a fcc lattice having a radius of $\sqrt{2}\stackrel{\circ }{A}$. What is the volume (in $c{m}^3$) of one unit cell?

1. $1.6\times {10}^{-22}c{m}^3$
2. $2.8\times {10}^{-24}c{m}^3$
3. $6.4\times {10}^{-23}c{m}^3$
4. $5.6\times {10}^{-24}c{m}^3$

Q. The radius of a divalent cation $A^{2+}$ is $94pm$ and that of a divalent anion $B^{2-}$ is $146pm$. The coordination number of $AB$ is:

1. 8
2. 4
3. 3
4. 6

Q.

A crystallizes in HCP close packing and B occupied $\frac{1}{2}$ of octahedral voids.

Calculate the formula of the compound?

What if 2 ions of A are removed from the corner of each unit cell?

What is the new crystal formula?

1. $A_{2}B,A_{17}{B}_9$ respectively

2. $A{B}_2,A_{17}B$respectively

3. $A_{3}B,A{B}_9$ respectively

4. $A_{4}B,A_{17}{B}_9$ respectively

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

1. $XY{Z}_2$
2. $X_{2}Y{Z}_2$
3. $X_8{Y}_4{Z}_5$
4. $X_5{Y}_4{Z}_8$

Q. In a cubic packed structure of a compound, the lattice is made up of oxide ions, one-fifth of the tetrahedral voids are occupied by X ions while half of the octahedral voids are occupied by Y ions. Then the formula of the oxide will be

1. $X_5{Y}_4{O}_{10}$
2. $X_4{Y}_5{O}_{10}$
3. $X{Y}_2{O}_4$
4. $X_{2}Y{O}_4$

Q. 34. How many triangular void formed at surface of octahedral void show

Q.

In ABAB close packing in 3-D, what are the types of voids present?

1. Tetrahedral voids

2. Octahedral voids

3. ABAB close packing

4. circular voids

Q.

Atoms of element B from HCP lattice and those of element A occupy two thirds of tetrahedral voids. What is the formula of the compound formed by elements A and B.

1. $A_4{B}_3$

2. $A_4{B}_6$

3. $A_8{B}_3$

4. $A_5{B}_3$

Q.

The structure of a mixed oxide is cubic close packed (ccp). The cubic unit cell of mixed oxide is composed of oxide ions. One-fourth of the tetrahedral voids are occupied by divalent metal A and the octahedral voids are occupied by a monovalent metal B. The formula of the oxide is

1. $AB{O}_2$

2. $A_{2}B{O}_2$

3. $A_2{B}_3{O}_4$

4. $A{B}_2{O}_2$

Q. Element ‘B’ forms ccp structure and ‘A’ occupies half of the octahedral voids, while oxygen atoms occupy all the tetrahedral voids. The structure of bimetallic oxide is:

1. $A_2{B}_{2}O$
2. $A{B}_2{O}_4$
3. $A_4{B}_{2}O$
4. $A_{2}B{O}_4$

Q. Minimum distance between two tetrahedral voids if a is the edge length of the cube is Options: (1) a/2 (2) a/4 (3) a/2√2 (4) √3a/4

Q. Atoms of an element crystalize in an FCC lattice that has an atomic diameter of $\sqrt{6}$ Å. What is the minimum distance between a tetrahedral void and an octahedral void (in Å)?

Q. If the unit cell of a mineral has cubic closed packing (CCP) array of oxygen atoms with $m$ fraction of octahedral holes occupied by aluminium ions and $n$ fraction of tetrahedral holes occupied by magnesium ions, $m$ and $n$, respectively, are

1. $\frac{1}{2},\frac{1}{8}$
2. $1,\frac{1}{4}$
3. $\frac{1}{2},\frac{1}{2}$
4. $\frac{1}{4},\frac{1}{8}$