Solid State Test

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Solid State Test - 22

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Weekly Quiz Competition

Question 1
1 / -0

Read the passage given below and answer the following questions:

In ideally ionic structures, the coordination numbers of the ions are determined by electrostatic considerations. Cations surround themselves with as many anions as possible and vice versa. This maximizes the attractions between neighbouring ions of opposite charge and hence maximizes the lattice energy of the crystal. This requirement led to the formulation of the radius ratio rule for ionic structures in which the ions and the structure adopted for a particular compound depend on the relative sizes of the ions. Thus, for the stable ionic crystalline structures, there is definite radius ratio limit for a cation to fit perfectly in the lattice of anions, called radius ratio rule. This depends upon the ratio of radii of two types of ions, r+/r–.
This ratio for coordination numbers 3, 4, 6 and 8 are respectively 0.155 – 0.225, 0.225 -0.414, 0.414 -0.732 and 0.732 – 1.000. The coordination number of ionic solids also depends upon temperature and pressure. On applying high pressure, coordination number increases. On the other hand, on applying high temperature, it decreases.

Q. If the radius of Nation is 95 pm and that of Cl– ion is 181 pm, the coordination number of Na+ ion is

A
6

B
4

C
8

D
12

Solution

The radius of the cation (r⁺) is 95 pm and the radius f the anion (r⁻) is 181 pm.
radius ratio = r⁺ / r^-
= 95 / 181
= 0.52
Since the radius ratio is in between 0.414 to 0.732, the coordination number of cations is 6.
Question 2
1 / -0

Study the diagram given below and answer the following questions:
In these questions, a statement of Assertion followed by a statement of Reason is given. Choose the correct answer out of the following choices.

Assertion (A): LiCl Crystal is pink.
Reason (R): Pink colour of LiCl crystal is due to excess Lithium.

A
Both A and R are true and R is the correct explanation of A

B
Both A and R are true but R is NOT the correct explanation of A

C
A is true but R is false

D
A is false and R is True

Solution

LiCl crystal is pink due to excess Lithium. It is caused by metal excess defect caused by a anionic vacancies(F-centres).
Question 3
1 / -0

Read the passage given below and answer the following questions:

In ideally ionic structures, the coordination numbers of the ions are determined by electrostatic considerations. Cations surround themselves with as many anions as possible and vice versa. This maximizes the attractions between neighbouring ions of opposite charge and hence maximizes the lattice energy of the crystal. This requirement led to the formulation of the radius ratio rule for ionic structures in which the ions and the structure adopted for a particular compound depend on the relative sizes of the ions. Thus, for the stable ionic crystalline structures, there is definite radius ratio limit for a cation to fit perfectly in the lattice of anions, called radius ratio rule. This depends upon the ratio of radii of two types of ions, r+/r–.
This ratio for coordination numbers 3, 4, 6 and 8 are respectively 0.155 – 0.225, 0.225 -0.414, 0.414 -0.732 and 0.732 – 1.000. The coordination number of ionic solids also depends upon temperature and pressure. On applying high pressure, coordination number increases. On the other hand, on applying high temperature, it decreases.

Q. Which is not the correct statement for ionic solids in which positive and negative ions are held by strong electrostatic attractive forces?

A
The radius ratio r+/r– increases as coordination number increases.

B
As the difference in size of ions increases, coordination number increases.

C
When coordination number is eight, r+/r– ratio lies between 0.225 to 0.414.

D
In ionic solid of the type AX (ZnS, wurtzite), the coordination number of Zn²⁺ and S^2- respectively are 4 and 4.

Solution

A) Radius ratio increases from 0.155-1 as coordination no. increases.
B) The difference in the size of ions increases as coordination number increases that is why in the CsCl structure having high coordination no. of 8, the size of the cation and anion is almost similar.
C) When the radius ratio lies between 0.225 to 0.414 then the coordination number is 4. Coordination no. is 8 when the radius ration is 0.732-1.
D) Statement is correct.
Option C is the correct answer.
Question 4
1 / -0

Study the diagram given below and answer the following questions:
In these questions, a statement of Assertion followed by a statement of Reason is given. Choose the correct answer out of the following choices.

Assertion (A): The crystal lattice density increases due to the defect shown in the diagram.
Reason (R): Tetrahedral voids are surrounded by 4 constituent particles.

A
Both A and R are true and R is the correct explanation of A

B
Both A and R are true but R is NOT the correct explanation of A

C
A is true but R is false

D
A is false and R is True

Solution

The crystal lattice density decreases due to the defect shown in the diagram-Schottky defect.
Question 5
1 / -0

Read the passage given below and answer the following questions:

In ideally ionic structures, the coordination numbers of the ions are determined by electrostatic considerations. Cations surround themselves with as many anions as possible and vice versa. This maximizes the attractions between neighbouring ions of opposite charge and hence maximizes the lattice energy of the crystal. This requirement led to the formulation of the radius ratio rule for ionic structures in which the ions and the structure adopted for a particular compound depend on the relative sizes of the ions. Thus, for the stable ionic crystalline structures, there is definite radius ratio limit for a cation to fit perfectly in the lattice of anions, called radius ratio rule. This depends upon the ratio of radii of two types of ions, r+/r–.
This ratio for coordination numbers 3, 4, 6 and 8 are respectively 0.155 – 0.225, 0.225 -0.414, 0.414 -0.732 and 0.732 – 1.000. The coordination number of ionic solids also depends upon temperature and pressure. On applying high pressure, coordination number increases. On the other hand, on applying high temperature, it decreases.

Q. If the pressure of CsCl is increased, then its coordination number will

A
increase

B
remain the same

C
decrease

D
none of these

Solution

NaCl crystal has 6:6 coordination number. When pressure is applied, ions come closer to each other. This gives a close packed (more compact) structure. The coordination number increases to 8:8 and the structure changes to CsCl type structure.