Select the correct option based on statements below:

The packing efficiency of the face-centered cubic unit cell is:
(assuming that the atoms are touching each other)

1. 52.40 %

2. 68.04 %

3. 74 %

4. 79.06 %

Silver crystallizes in fcc lattice. If the edge length of the cell is 4.07 × 10⁻⁸ cm and density is 10.5 g cm⁻³, the atomic mass of silver is -

1. 120.31 g ${\mathrm{mol}}^{-1}$

2. 107.9 g ${\mathrm{mol}}^{-1}$

3. 207.60 g ${\mathrm{mol}}^{-1}$

4. 138.52 g ${\mathrm{mol}}^{-1}$

An element with a molar mass of 2.7 × 10^-2 kg mol^-1  and density  2.7 × 10³ kg m^-3  forms a unit cell with an edge length of 405 pm. The type of unit cell is-

1. Simple cubic cell.

2. Face-centered cubic cell.

3. Body-centered cubic cell.

4. None of the above.

A compound is formed by two elements M and N. The element N forms ccp and atoms of M occupy 1/3rd of tetrahedral voids. The formula of the compound would be -

1. MN

2. M₃N₄

3. M₂N₃

4. M₃N₂

A ferric oxide crystallizes in a hexagonal close-packed array of oxide ions with two out of every three octahedral holes occupied by ferric ions. The formula of the ferric oxide is-

1. FeO

2. Fe₂O₃

3. Fe₃O₄

4. Fe₃O₂

 The pair having only molecular solids among the following is -

1. Brass and SiC

2. Ammonium phosphate (NH₄)₃PO₄

3. SiC and plastic 

4. Tetra phosphorus decaoxide (P₄O₁₀) and I₂

Nickel oxide has the formula Ni_0.98O_1.00. The fraction of nickel existing as Ni³⁺ ions will be -

1. 0.041

2.  0.959

3. 0.736 

4. 0.264 

A compound forms a hexagonal close-packed structure. The total number of voids in 0.5 moles

of the compound will be -

$1.$ $9.033$ $\times$ ${10}^{23}$
$2.$ $3.011$ $\times$ ${10}^{23}$
$3.$ $6.023$ $\times$ ${10}^{23}$
$4.$ $8.024$ $\times$ ${10}^{23}$

Copper crystallizes into an fcc lattice with an edge length of 3.61 × 10⁻⁸ cm. The density of copper crystal will be - 

1. 7.46 g cm^-3

2. 9.67 g cm^-3

3. 8.96 g cm^-3

4. 5.63 g cm^-3