NCERT Class 12 Chemistry Solutions The Solid State

NCERT Class 12 Chemistry Solutions The Solid State - NCERT Solutions prepared for CBSE students by the best teachers in Delhi. 

Class XII  Chemistry

Chapter 1 – The Solid State

Question 1:

Define the term 'amorphous'. Give a few examples of amorphous solids.


Amorphous solids are the solids whose constituent particles are of irregular shapes and have short range order. These solids are isotropic in nature and melt over a range of temperature. Therefore, amorphous solids are sometimes called pseudo solids or super cooled liquids. They do not have definite heat of fusion. When cut with a sharp-edged tool, they cut into two pieces with irregular surfaces. Examples of amorphous solids include glass, rubber, and plastic.


Question 2:

What makes a glass different from a solid such as quartz? Under what conditions could quartz be converted into glass?


The arrangement of the constituent particles makes glass different from quartz. In glass, the constituent particles have short range order, but in quartz, the constituent particles have both long range and short range orders. Quartz can be converted into glass by heating and then cooling it rapidly.


Question 3:

Classify each of the following solids as ionic, metallic, molecular, network (covalent) or amorphous.

(i) Tetra phosphorus decoxide (P4O10)                                                           (vii) Graphite

(ii) Ammonium phosphate (NH4)3PO4                                                            (viii) Brass

(iii) SiC                                                                                                                     (ix) Rb

(iv) I2                                                                                                                         (x) LiBr

(v) P4                                                                                                                         (xi) Si


Ionic → (ii) Ammonium phosphate (NH4)3PO4,                      (x) LiBr

Metallic → (viii) Brass,                                                                    (ix) Rb

Molecular → (i) Tetra phosphorus decoxide (P4O10),             (iv) I2,                                            (v) P4.

Covalent (network) → (iii) SiC,                                                      (vii) Graphite,                               (xi) Si

Amorphous → (vi) Plastic


Question 4:

(i) What is meant by the term 'coordination number'?

(ii) What is the coordination number of atoms:

(a) in a cubic close-packed structure?

(b) in a body-centred cubic structure?


(i) The number of nearest neighbours of any constituent particle present in the crystal lattice is called its coordination number.

(ii) The coordination number of atoms

(a) in a cubic close-packed structure is 12, and

(b) in a body-centred cubic structure is 8


Question 5:

'Stability of a crystal is reflected in the magnitude of its melting point'. Comment. Collect melting points of solid water, ethyl alcohol, diethyl ether and methane from a data book. What can you say about the intermolecular forces between these molecules?


Higher the melting point, greater is the intermolecular force of attraction and greater is the stability. A substance with higher melting point is more stable than a substance with lower melting point.

The melting points of the given substances are:

Solid water ¨ 273 K

Ethyl alcohol ¨ 158.8 K

Diethyl ether ¨ 156.85 K

Methane ¨ 89.34 K

Now, on observing the values of the melting points, it can be said that among the given substances, the intermolecular force in solid water is the strongest and that in methane is the weakest.

Question 6:

How will you distinguish between the following pairs of terms:

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

(ii) Crystal lattice and unit cell?

(iii) Tetrahedral void and octahedral void?


(i). A 2-D hexagonal close-packing contains two types of triangular voids (a and b). Let us call this 2-D structure as layer A. Now, particles are kept in the voids present in layer A (it can be easily observed from figures 2 and 3 that only one of the voids will be occupied in the process, i.e., either a or b). Let us call the particles or spheres present in the voids of layer A as layer B. Now, two types of voids are present in layer B (c and d). Unlike the voids present in layer A, the two types of voids present in layer B are not similar. Void c is surrounded by 4 spheres and is called the tetrahedral void. Void d is surrounded by 6 spheres and is called the octahedral void.


Students should free download the NCERT solutions and get better marks in exams. panel of teachers recommend students to practice questions in NCERT books and download NCERT solutions.



Click to View or Download pdf file
Click for more Chemistry Study Material

Latest NCERT & CBSE News

Read the latest news and announcements from NCERT and CBSE below. Important updates relating to your studies which will help you to keep yourself updated with latest happenings in school level education. Keep yourself updated with all latest news and also read articles from teachers which will help you to improve your studies, increase motivation level and promote faster learning

Keep your kids engaged during Lockdown

Kids are the Future of our Country! Outlines have changed and so should the formats of existence! It is the best time to teach our kids the pleasure of Self-Discipline, Self-Realization and Self-Control. To keep the future generation safe in such unpredictable...

Training of CBSE School Teachers on Olabs

Training of CBSE School Teachers on Olabs in collaboration with C-DAC Mumbai: OLabs is a platform jointly developed by the Ministry of Electronics and Telecommunications, Government of India, CDAC, and Amrita University to facilitate a virtual experience of CBSE...

Revised SOP preventive measures followed while conducting examinations

Revised SOP on preventive measures to be followed while conducting examinations to contain spread of COVID-19 issued by Ministry of Health & Family Welfare Examination centres are frequented by large number of students (as well as their parents) and staff till the...

NEP Transforming India Quiz

As a part of Shikshak Parv celebration, an online quiz competition on National Education Policy 2020 will be organized by the Ministry of Education, Govt. of India, from 5 th September to 25th September 2020 in order to create awareness about NEP among all stakeholders...

Conduct of the practical work during the lockdown

CBSE has advised schools to follow the Alternative Calendar developed by NCERT to continue education during the lockdown through alternative modes to achieve learning outcomes. Schools have reportedly started using these calendars and other prescribed pedagogical...

TERI Green Olympiad 2020

Green Olympiad is a value driven project conducted by TERI (The Energy and Resources Institute) for school students annually since 1999. This Olympiad assesses the environment quotient of students and also enhances their understanding on issues related to sustainable...

Studies Today