Zeff

Q.

Ga (atomic mass $70\mathrm{u}$) crystallizes in a hexagonal close-packed structure. The total number of voids in $0.581\mathrm{g}$ of $\mathrm{Ga}$ is ________ $\times {10}^{21}$. (Round off to the nearest integer). [Given: ${\mathrm{N}}_{\mathrm{A}}=6.023\times {10}^{23}$].

Q.

$CsBr$ crystallises in a bcc lattice. The unit cell length is 436.6 pm. Given that the atomic mass of Cs=133 and that of Br=80 amu and Avogadro no. being 6.02310 per mol the density of $CsBr$ is? 42.5 g/cc 0.425 g/cc 8.25 g/cc 4.25 g/cc

Q.

The number of atom in 100g of an FCC crystal with density d=10g/cm3 and cell edge equal to 100 pm is equal to

Q. An element has a body-centred cubic $\left(bcc\right)$ structure with a cell edge of $288pm$. The density of the element is $7.2gc{m}^{-3}$. How many atoms are present in $208g$ of the element ?

Q. Assertion: Toxic metal ions are removed by the chelating ligands.

Reason: Chelate complexes tend to be more stable.

1. Assertion is false, reason is true.
   

2. Assertion and reason both are true, reason is correct explanation of assertion.

3. Assertion and reason both are true but reason is not the correct explanation of assertion.
   
4. Assertion is true, reason is false.
   

Q. The number of tetrahedral and octahedral voids in hexagonal primitive unit cell are

1. 8, 4

2. 2, 1

3. 12, 6

4. 6, 12

Q.

If one of the atoms is removed from a simple cubic unit cell the effective number of atoms remaining in a unit cell is

Q.

In a face-centered cubic lattice, a unit cell is shared equally by how many unit cells

1. 8

2. 4

3. 2

4. 6

Q.

In $\mathrm{CsCl}$ type structure, the coordination number of ${\mathrm{Cs}}^{+}$ and ${\mathrm{Cl}}^{-}$ respectively are:

1. 6, 6

2. 6, 8

3. 8, 6

4. 8, 8

Q.

A compound formed by elements X and Y crystallizes in the cubic structure where Y atoms are at the corners of the cube and X atoms are at the alternate faces. What is the formula of the compound?

Q.

How many unit cells are present in 39g of potassium that crystallizes in a BCC structure

I don't understand the method of solution???

Q. Why do end centred lattices exist only in orthorhombic and monoclinic bravais lattices

Q.

What is the distinguishing layer between hexagonal close packing and cubic close packing?

1. Second layer

2. First layer

3. Third layer

4. All layers

Q. At room temperature, polonium crystallises in Cubic primitive cell. If edge length is 3.0\overset0A calculate the theoretical density of Po.(Atomic weight of Po=207g

Q. A compound $M_p{X}_q$ has cubic close packing (ccp) arrangement of X. Its unit cell structure is shown below. The empirical formula of the compound is

1. MX
2. $M{X}_2$
3. $M_{2}X$
4. $M_5{X}_{14}$

Q. Volume occupied by molecules of one mole gas at N.T.P., each having radius of ${10}^{-8}$ cm

1. 220 litre
2. 22.4 litre
3. 10.09 litre
4. 10.09 ml

Q. NACL FORMS AN IONIC CRYSTAL IN WHICH CL- IONS FORM CCP LATTICE . THE NO OF NA+ IONS PRESENT AT A DISTANCE OF ROOT 5/2 A FROM CL- ION AT THE CORNER IS [HERE A IS THE EDGE LENGTH OF CRYSTALS]

Q.

Does a FCC Tetragonal unit cell exist?

Q.

Compute the percentage void space per unit volume of unit cell in zinc-fluride structure. In zinc fluoride, anions occupy

fcc positions and half of the tetrahedral holes are occupied by cations.

1. 25%

2. 30%

3. 40%

4. 20%

Q. In an oxide, oxide ions are packed in an FCC unit cell in which $B^{3+}$ ions occupy x% of octahedral voids and $A^{2+}$ ions occupy y% of tetrahedral voids, then which of the following is/are correct about the unit cell?

1. Formula is $A_{2}B{O}_8$ in which x= 12.5% and y= 12.5%
2. Formula is $A_2{B}_4{O}_6$ in which x= 50% and y= 50%
3. Formula is $A{B}_2{O}_4$ in which x= 50% and y= 12.5%
4. Formula is $A_{2}B{O}_2$ in which x= 12.5% and y= 50%

Q. Q. Ice crystallises in a hexagonal lattice having the volume of a unit cell as 132x10^-24. If the density is 0.92g/cm^3 at a give temp., Then the number of H2O molecules per unit cell is:- Options: 1. 1 2. 2 3. 3 4. 4 -------------------------------------- According to the solution, the value of Z has been found. But we know that Z is the number of atoms, which is 4 for hcp. Then how come Z is taken as number of molecules of H2O ??

Q.

An element with a molar mass of 27 g/mol forms a cubic unit cell with an edge length of 4.05 ×10^-8 cm. If the density of the element is 2.7 g/cm^-3. What will be the nature of a cubic unit cell?

1. Face Centred Cubic (FCC)

2. Cubic-Close packed (CCP)

3. Body-Centred Cubic (BCC)

4. Both (A) and (B)

Q.

Calculate the ionic radius of a Cs⁺ ion assuming the cell edge length for CsCl is 0.4123 nm and that the ionic radius of a Cl^- ion is 0.181 nm.

1. 0.176 nm

2. 0.116 nm

3. 0.358 nm

4. 0.231 nm

Q.

An element with bcc geometry has atomic mass 50 and edge length 290 pm. The density of unit cell will be

1. 8.16 g/cm³

2. 6.81 g/cm³

3. 68.1 g/cm³

4. 1.86 g/cm³

Q.

(a) Arrange the following as per the instructions given in the brackets
(ii) Mg, Cl, Na, S, Si (Decreasing order of atomic size)

Q. A cubic solid has two elements A and B. Atoms A occupy the corners and atoms B occupy the alternate edge centres of the unit cell. The formula of the compound is

Q. An element A crystallises in fcc structure.200g of this element has 4.12×10^2 atoms.the density of A is 7.2g/cm^3.Calculate the edge lenght of the unit cell.eq

Q.

An atom present at the face centre is shared by how many unit cells?

1. 5

2. 4

3. 3

4. 2

Q.

Q8) An element having atomic mass 60 has FCC unit cells .the edge length of the unit cell is 400pm .find the density of the element

Q.

Define empirical formula and molecular formula of a compound.