Crystal Lattice and Unit Cell

Q. The intermetallic compound LiAg crystallizes in cubic lattice in which both lithium and silver have coordination number of eight. The crystal class is

1. Simple cube

2. Body-centred cube

3. Face-centred cube

4. None of these

Q.

How do I Convert Molecules to Moles?

Q.

What is the value of z for a body-centred unit cell?

Q. Which of the following statement(s) is/are incorrect regarding tetrahedral voids in fcc lattice?

1. Each body diagonals contains 2 tetrahedral voids.
2. Each tetrahedral void contributes $\frac{1}{4^{th}}$ part to a unit cell
3. One tetrahedral void is present at the body centre of unit cell
4. Each face diagonals contains 2 tetrahedral voids

Q.

What is the concept of range order ?

Q.

What is the difference between the coordination entity and the coordination sphere?

Q.

How will you distinguish between the following pair of terms :

(i) hexagonal close-packing and cubic close-packing?

(ii) crystal lattice and unit cell ?

(iii) tetrahedral void and octahedral void?

Q.

What is the coordination number in body centered cubic (BCC) arrangement of identical particles?

Q. In the rock salt structure, the number of formula units per unit cell is equal to

1. 2
2. 3
3. 1
4. 4

Q.

Give the significance of a ‘lattice point’.

Q. An ionic compound AB has $ZnS$ (Zinc blende) type structure. If the radius $A^{+}$ is $22.5pm$, then the ideal radius of $B^{-}$ would be

1. $54.35pm$
2. $100pm$
3. $145.16pm$
4. none of these

Q. An element crystallizes in a FCC lattice with cell edge of 400 pm. The density of the element is $7gc{m}^{-3}$. How many atoms are present in 280 g of the element?

Q. Covalent bonds are directional, while ionic bonds are non-directional, why.?

Q. For 3-D hexagonal closed packing structure (with similar particles), the correct relation between radius of atoms (r) and height of unit cell (h) is :

1. $h=\sqrt{\frac{2}{3}}\times 2r$
2. $h=\sqrt{\frac{2}{3}}\times 4r$
3. $h=\sqrt{\frac{3}{2}}\times 2r$
4. $h=\sqrt{\frac{3}{2}}\times 4r$

Q. 23.Which of the following statements is not correct (1)The number of bravais lattices in which a crystal can be categorized is 14 (2)The fraction of the total volume occupied by the atoms in a primitive cell is 0.52 (3)Molecular solids are generally volatile (4)The number of carbon atoms in a unit cell of diamond is 4

Q. Which of the following statement(s) is/are true regarding monoclinic crystal system?

1. All the 3 edge lengths are different
2. Two of the edge lengths are same
3. Two of the axis angles are equal to ${120}^o$
4. All the axial angles are different

Q. What type of stoichiometric defect is shown by:
A.$\text{ZnS}$
B.$\text{AgBr}$

Q.

An element M has an atomic number 9 and atomic mass 19. Its ion will be represented by

1. M

2. M⁺²

3. M^-

4. M^-2

Q.

For the orthorhombic system, axial ratios are $\mathrm{a}\ne \mathrm{b}\ne \mathrm{c}$, and the axial angles are:

1. $\mathrm{\alpha }=\mathrm{\beta }=\mathrm{\gamma }\ne 90$ degree

2. $\mathrm{\alpha }=\mathrm{\beta }=\mathrm{\gamma }=90$ degree

3. $\mathrm{\alpha }\ne \mathrm{\beta }=\mathrm{\gamma }=90$ degree

4. $\mathrm{\alpha }\ne \mathrm{\beta }\ne \mathrm{\gamma }=90$degree

Q.

The packing fraction of the element that crystallizes in simple cubic arrangement is:

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

Q.

The vacant space in the bcc unit cell is -

Q.

Explain the dipole-dipole interaction energy between stationary polar molecules.

Q.

What is Z Value in Crystallography?

Q. Question 2.23:

Suggest the most important type of intermolecular attractive interaction in the following pairs.

(i)n-hexane and n-octane

(ii)I₂and CCl₄

(iii)NaClO₄and water

(iv)methanol and acetone

(v)acetonitrile (CH₃CN) and acetone (C₃H₆O).

Answer:

(i) Van der Walls forces of attraction.

(ii) Van der Walls forces of attraction.

(iii) Ion-diople interaction.

(iv) Dipole-dipole interaction.

(v) Dipole-dipole interaction.

how will i know if it is van der waals force?

Q. In CCP of n spheres of radius r, n spheres of radius 0.414 r and 2n spheres of radius 0.225 r are introduced in the octahedral and tetrahedral void respectively. Therefore, packing fraction of the lattice is:

1. 0.7
2. 0.81
3. 0.68
4. 0.9

Q. How will you distinguish between the following pairs of terms :

(i) Tetrahedral and octahedral voids

(ii) Crystal lattice and unit cell

Q.

Percentage of free space in a BCC unit cell is ?

1. $32\%$

2. $34\%$

3. $28\%$

4. $30\%$

Q. The following figure shows the unit cell of a compound, i.e., a mixed oxide of yttrium, barium and copper. The formula of mixed oxide is $Y_{a}B{a}_{b}C{u}_c{O}_d$.

Find the value of $a+b+c+d$.

Q. Each rubidium halide crystallising in the $NaCl$ type lattice has a unit cell length $0.30\stackrel{\circ }{A}$ greater than that for corresponding potassium salt. $(r_{\left(K^{+}\right)}=1.33\stackrel{\circ }{A})$ of the same halogen. Hence, ionic radius of $R{b}^{+}$ is:

Q.

What kind of forces exists between adsorbate and adsorbent in chemical adsorption?

1. Vander Waal’s forces

2. Covalent bonding

3. Ionic bonding

4. both (B) and (C)