NCERT Solutions for Class 12 Chemistry Chapter 1

NCERT Solutions for Class 12 Chemistry Chapter 1 The Solid State

As we know, there are three states of matter: solid, liquid, and gas. In this chapter of the NCERT book, you will be introduced to different types of structures of solids that exist in nature. E.g., NaCl has a cubic structure, and Graphite has a hexagonal structure. At the end of the Extramarks NCERT Solutions for Class 12 Chemistry Chapter 1, you will also come to know the defects in these solid structures. These defects in the solids also introduce some magnetic properties. 

NCERT Solutions for Class 12 Chemistry Chapter 1 – The Solid State is prepared in a very comprehensive manner. These solutions help students to grasp the topic thoroughly. By referring to the NCERT solutions for Class 12, students can understand all the essential concepts and practice questions well before their examination.

The key topics covered in NCERT solutions class 12 Chemistry chapter 1 include

Students may click on the respective exercise of NCERT Solutions For Class 12 Chemistry Chapter 1 to access study materials. The Solid State NCERT Solution that we provide can help students prepare well for their examinations.

Below is the brief of the Chemistry class 12 NCERT solutions chapter 1.

1.1 Introduction

Solids mostly surround us, and we use them more often than liquids and gases. Three states of matter are – solid, liquid and gas. Some of the properties of solids are:

• Solids have a specific volume, mass and shape.
• Distance and force: Intermolecular distance is short, as intermolecular force is strong
• Solids are rigid and incompressible
• Particles have fixed positions

1.2 Classification of crystalline solids

Under this section of the NCERT solutions class 12 Chemistry chapter 1, students will learn about the classification of crystalline solids. A solid interface is explained as a few atomic layers that separate two solids in intimate contact. The properties differ remarkably from those of the bulk material it separates.

Based on crystal structures, solids can be categorised as Amorphous and crystalline solids.

Crystalline solids: They have a specific geometric shape and have long-range order. These are isotropic and do not have definite heat of fusion. Examples of crystalline solids are diamond, sodium nitrate and sodium chloride. Crystalline solids are also called true solids. However, crystalline solids can be classified into molecular, ionic, metallic, and covalent. 

Amorphous Solids: The solids in which the particles are arranged irregularly and solids that lack the overall sequence of a crystal lattice are known as amorphous solids. The amorphous word came from the Greek ‘amorphous’, which means no form. The particles are of indefinite shape as well as have no long-range order. An amorphous solid example is Quartz glass, gels, and nanostructured materials. Amorphous solids are also known as supercooled or pseudo solids. Students may refer to NCERT Solutions for Class 12 Chemistry Chapter 1 Exercise 1.2 to grasp all the key concepts in detail.  

Key Features of Crystalline and Amorphous Solids

The key features of crystalline and amorphous solids are a part of NCERT Solutions For Class 12 Chemistry Chapter 1 and include

Nature

• Crystalline Solids – True Solids
• Amorphous Solids – Pseudo – Solids as well as supercooled liquids.

Geometry

• Crystalline Solids – Here, the particles are arranged in a repeating pattern. They have a regular arrangement resulting in a definite shape.
• Amorphous Solids – Particles are not appropriately arranged. They have an irregular arrangement resulting in indefinite shape.

Melting Points

• Crystalline Solids – melt at a sharp melting point temperature
• Amorphous Solids – Gradually soften gradually over a  range of temperatures

Heat of Fusion

• Crystalline Solids – They have definite and characteristic heat of fusion.
• Amorphous Solids – Here, they do not have definite heat of fusion

Isotropism

• Crystalline Solids – Anisotropic in nature.
• Amorphous Solids – Isotropic in nature.

Cleavage Property

• Crystalline Solids – When cutting using a tool with a sharp edge, split into two new halves pieces, and the newly generated surfaces are plain.
• Amorphous Solids – When cutting using a tool with a sharp edge, they cut into two pieces with irregular surfaces

Rigidity

• Crystalline Solids are rigid solids, and applying mild forces can’t change their shape.
• Amorphous Solids – They are not rigid, so mild effects may change the shape.

Students may refer to NCERT Solutions For Class 12 Chemistry Chapter 1 for detailed study material on Solid State.

1.3Crystal Lattices and Unit cells

Under this exercise of chapter 1 Chemistry class 12 NCERT solutions, students will learn about the following.

Unit Cell: The smallest repeating pattern of the crystal lattice is the unit cell, the building block of a crystal.

Types Of Unit Cell: An entire lattice can be obtained by repeating a small portion known as the unit cell. Different varieties of the unit cell are as under. 

1. Primitive Cubic Unit Cell
2. Body-centred Cubic Unit Cell
3. Face centred cubic unit cell

Crystal Lattices

A crystal structure comprises atoms and lattice points or lattice axes. Significantly, the structure is an ordered array of atoms, ions or molecules.

The main characteristics of Crystal Lattice:

• Each point in a lattice is known as a lattice point or site.
• Each point in a crystal lattice indicates one constituent particle, which may be an atom, molecule or ion.
• Lattice points are attached by straight lines to bring out the geometry of the lattice.

1.4 Number of Atoms in a Unit Cell

Under this exercise of NCERT Solutions For Class 12 Chemistry Chapter 1, students will learn about atoms in a unit cell.

Primitive unit cell: The primitive cubic unit cell contains atoms only at its corner. Each atom at a corner is shared among eight adjacent unit cells, four-unit cells on the same side and four-unit cells on the upper or lower side. Hence, only 1/8th of an atom belongs to a particular unit cell.

Body Centred unit Cell: A body-centred cubic unit cell contains an atom at each corner and one at its body centre.

Number of Atoms in BCC Cell:

Thus, in a BCC cell, we have

• 8 corners × 1/8 per corner atom = 8 × 1/8 = 1 atom
• 1 body centre atom is = 1 × 1 = 1 atom

Hence, the exact number of atoms present per unit cell = 2 atoms.

Face-Centred unit Cell: A face-centred unit cell contains atoms at every corner and the centre of all the faces of the cube. The atom present at the face centre is shared among two adjacent unit cells; only 1/2 of each atom belongs to the unit cell (see Figure 1).

Number of Atoms in BCC Cell

• 8 corners × 1/8 per corner atom = 8 × 1/8 = 1 atom
• 6 face-centred atoms × 1/2 atom per unit cell = 3 atoms

Hence, the total number of atoms per unit cell = 4 atoms. Students can refer to NCERT Solutions For Class 12 Chemistry Chapter 1 for more information on the number of Atoms in a Unit Cell.

1.5 Close Packed Structures

Under Exercise 1.5 of the NCERT Solutions For Class 12 Chemistry Chapter 1, students will study that the constituent particles are close-packed in a solid state, leaving the minimum vacant space.

(a) Close Packing in One Dimension: In close packing of one dimension, spheres are arranged in a row such that adjacent atoms are in contact with each other. The coordination number is explained as the no. of nearest neighbour particles. In the case of one-dimensional close packing, the coordination number equals 2.

(b) Close packing in Two Dimensions: The two-dimensional close-packed structure can be generated by stacking the row of closed packed spheres. Students can refer to Extramarks NCERT Solutions For Class 12 Chemistry Chapter 1 for study material on the exercise. Closed packing in two dimension stacking is done in two ways, Hexagonal close-packing and cubic close packing, as shown in the figure below. 

The Formula of a Compound and the Number of Voids Filled

Voids mean space between the constituent particles. Voids represent the vacant space between the constituent particles in a closely packed structure in solid states. The 3D structure has two types of interstitial voids, Tetrahedral voids and Octahedral voids.

1.6 Packing Efficiency

As per NCERT Solutions For Class 12 Chemistry Chapter 1, Packing Efficiency is the percentage of the total place occupied by the particles.

Packing Efficiency in hcp and ccp Structures: Both Hexagonal close packing (hcp) and cubic close packing (ccp) have the exact packing efficiency

We can also write it as

Packing efficiency = volume occupied by four spheres in the unit cell x 100

                                            The total volume of the unit cell

Students may refer to class 12 Chemistry NCERT solutions chapter 1 to know more.

1.7 Calculations Involving Unit Cell Dimensions

The unit cell can be understood as a three-dimensional structure consisting of one or more atoms. The volume of this unit cell can be calculated using unit cell dimensions. 

Mass of unit cell = the number of atoms in unit cell × mass of each atom = z × m

In the above formula, z = number of atoms in the unit cell and m = mass of each atom

The mass of an atom can be given with the help of Avogadro number and molar mass as:

M/NA

Where M = molar mass

NA = Avogadro’s number

The volume of the unit cell, V = a3

=> Density of unit cell = mass of unit cell/ volume of the unit cell

=> Density of unit cell = m/V = z×ma/a3 = z×M/a3×NA

Students may refer to NCERT Solutions For Class 12 Chemistry Chapter 1 Exercise 1.7 to know more.

1.8 Imperfections in Solids

Point defects explain the imperfections of solids and the types of point defects. Point defects are accounted for when the crystallization process occurs at a very fast rate. These defects mainly happen due to deviation in the arrangement of constituting particles. The flaws are of two types, point defects and line defects.

Point defects are irregularities or deviations from the ideal arrangement around a point or an atom in a crystalline substance. On the other hand, Line defects are irregularities or deviations from an ideal arrangement in entire rows of lattice points. These irregularities are called crystal defects. 

Under NCERT Solutions  Class 12 Chemistry Chapter 1, Point defects can be classified into

• Stoichiometric defect – The ratio of positive and negative ions (Stoichiometric) and electrical neutrality of a solid are not disturbed in this kind of point defect. Sometimes it is also known as thermodynamic or intrinsic defects. Primarily, they are of two types: Vacancy defect and Interstitial defect
• Frenkel defect –This defect is generally shown in ionic solids; the smaller ion (cation) moves out of its place and occupies an intermolecular space. A vacancy defect is created in its original position, and the interstitial defect is experienced at its new location.

1.9 Electrical and Magnetic Properties

Under NCERT Solutions For Class 12 Chemistry Chapter 1, solids can be described into three types based on their conductivities. They are:

• Conductors
• Insulators
• Semiconductors

Magnetic properties are the study of Magnetic Materials. The material is generally placed in a uniform magnetic field, and then the magnetic field is varied. 

There are five major kinds of magnetic behaviour:

• Diamagnetic materials
• Paramagnetic materials
• Ferromagnetic materials
• Antiferromagnetic materials
• Ferrimagnetic materials

For a detailed description of electrical and magnetic properties, students can refer to NCERT Solutions  Class 12 Chemistry Chapter 1 provided by Extramarks. 

NCERT Solutions Class 12 Chemistry Chapter 1 Article Link

NCERT solutions class 12 Chemistry chapter 1 is explained in detail by the experts of Extramarks. In addition to chapter 1, students can access NCERT Solution for all other Chemistry chapters of class 12. Furthermore, students can click on the links provided below to access the study material of different classes.

NCERT Solution Class 11

NCERT Solution Class 10

NCERT Solution Class 9

NCERT Solution Class 8

NCERT Solution Class 7

NCERT Solution Class 6

NCERT Solution Class 5

NCERT Solution Class 4

NCERT Solution Class 3

NCERT Solution Class 2

NCERT Solution Class 1

In addition to NCERT Solutions For Class 12 Chemistry Chapter 1, students may also access various other study materials such as past year questions papers, revision notes, important questions and more on Extramarks.