Plus Two Chemistry Chapter Wise Previous Questions Chapter 1 The Solid State is part of Kerala Plus Two Chemistry Chapter Wise Previous Year Questions and Answers. Here we have given Plus Two Chemistry Chapter Wise Questions and Answers Chapter 15 Polymers.
Kerala Plus Two Chemistry Chapter Wise Previous Questions and Answers Chapter 1 The Solid State
What is the coordination number of particles present in the FCC crystal structure? [March 2018]
12 (fee = cep, for ccp.C.N = 12)
a. Based on the nature of intermolecular forces, classify the I following solids: [March 2018]
b. ZnO turns yellow on heating. Why?
i. Covalent or Network Solid
ii. Molecular’solid (Hydrogen bonded Molecular solid)
b. This is due to the metal excess defect due to extra cation or due to the presence of interstitial electron.
a. Identify’ the nonstoichiometric defect
i. Schottky defect
ii. Frenkel defect
iii. Interstitial defect
iv. Metal deficiency defect
b: What type of substance could make better permanent magnets ferromagnetic or ferrimagnetic? Justify your answer.
c. In terms of Band theory write the differences between conductor and insulator. [March 2017]
a. Metal deficiency defect
b. Ferromagnetic substance makes better permanent magnets because, in a solid state, the metal ions of ferromagnetic substances are grouped together into small regions called domains. Thus, each domain acts as a tiny magnet. In an unmagnetised piece of a ferromagnetic substance, the domains are randomly oriented and their magnetic moments get cancelled. When the substance is placed in a strong magnetic effect is produced. This ordering of domains persists even when the magnetic field is removed and the ferromagnetic substance becomes a permanent magnet. However, this is not possible in ferrimagnetic substances.
c. In conductors, the valence band and conduction band overlap. Hence electrons can easily flow. In insulators the energy gap between the valance band and the conduction band is large, then electrons cannot jump from one band to the other.
i. Which of the following is a molecular solid?
ii. Unit cells can be classified into primitive and centred unit cells. Differentiate between primitive and centred unit cells.
iii. Presence of excess sodium makes NaCI crystal coloured. Explain on the basis of crystal defects. [March 2016]
i. c. Ice
ii. In primitive unit cells, constituent particles are present only on the corner position of unit cell whereas in a centred unit cell, one or more, constituent particles are present at a position other than corners in addition to those at corners.
iii. Presence of excess sodium makes NaCI crystal coloured, this is caused by metal excess defect due to anionic vacancies. When NaCI crystal heated in an atmosphere of sodium vapour, the sodium atoms are deposited on the surface of the crystal and combine with Na atoms to give NaCI. The released electrons diffuse into the crystal and occupy anionic sites. As a result of the crystal now has an excess of sodium. The anionic sites occupied by unpaired electrons are F centres. They impart a yellow colour to the crystals of NaCI.
Unit cells can be divided into two categories, primitive and centred unit cells.
a. Differentiate between the unit cell and crystal lattice.
b. Calculate the number of atoms per unit cell in the following:
i. Body centred cubic unit cell (bcc)
ii. Face centred cubic unit cell (fee) [March 2015]
a. A crystal lattice may be defined as a regular three-dimensional arrangement of identical points in space. A unit cell may be defined as a three-dimensional group of lattice points that generates the whole crystal lattice when repeated regularly (unit cell is the smallest repeating unit of the crystal lattice).
i. Simple cubic cell: Contribution by 8 particle present at 8 corners
No. of the particle in simple cubic cell = 1
ii. Body centred cubic cell: Contribution by 8 particle resent at 8 corners Contribution by particle present in the body
No. of particle in body centred cubic cell = 1 + 1 = 2
iii. Face centred cubic cell: Contribution by 8 particle present at corners Contribution by 6 particle present on the centre of six faces
No. of the particle in a face centred cubic I cell 3 + 1 = 4
a. Every substance has some magnetic properties associated with it. How will you account for the following magnetic properties?
i. Paramagnetic property
ii. Ferromagnetic property
b. A compound is formed by two elements P and Q. Atoms of Q (as anions) make HCP lattice and those, of the element P (as cations) occupy all the tetrahedral voids. What is the formula of the compound? [March 2014]
a. i. Paramagnetic property is the property formed by the substance as it is weakly attracted by the magnetic field (m.field). Magnetic alignments are in the same direction,
Eg., O2, Fe3+.
ii. Ferromagnetic property is the property formed by the substance due to strongly attracted by the magnetic field. Magnetic alignments are in the same direction,
Eg., Co, Ni.
b. No. of atoms of Q = N
No. of atoms of P = 2N
∴ The ratio of atoms of P and Q =2:1
∴ The formula = P2Q
A crystal has an ordered arrangement of constituent particles.
a. Define the term unit cell.
b. Calculate the number of atoms in simple cubic and body centred unit cells.
c. Copper crystal has a face centred cubic lattice structure. Its density is 8.93gcnr-3.
What is the length of the unit cell? Atomic mass of copper is 63.5 gmol-1. [Model 2014]
a. A unit cell is the smallest repeating unit of crystal lattice which when repeated regularly in all directions results in the entire lattice.
b. Simple cubic/primitive unit cell particles present only at the corners.
∴ Total no. of particles
Body centred unit cell/cubic particles present at both corners and centre of the body.
∴ Total particles 1 = 2
c. M = 63.5 g/mol, d = 8.93,
NA = 6.022 × 1023
For face central cubic lattice,
a. NaCI has fcc structure. Calculate the number of NaCI units in a unit cell of NaCI.
b. Calculate the density of NaCI, if edge length of NaCI unit celt is 564 pm. [Molar mass of NaCI = 58.5 gmol-1]. [March 2013]
a. A fee structure has particles at the corners and at the face centres.
No. of particles at the corners
No. of particles at the face centres
Total number of particles per unit cell = 1 + 3 = 4 particles.
b. M = 58.5, Z=4,
a= 564 pm = 564 × 10-8 cm ZM
i. Name three types of solids classified on the basis of electrical conductivities.
ii. How will you explain such classification on the basis of Band theory? [March 2012]
i. Conductors, semiconductors and insulators.
ii. In conductors, the valence band and conduction band overlap. Hence electrons can easily flow. If the gap between the valence band and the conduction band is small, then some electrons may jump from the valence band to the conduction band. Therefore these substances show some conductivity and they are semiconductors. In insulators the energy gap between the valence band and the conduction band is large, then electrons cannot jump from one band to the other.
Write any two differences between Schottky defect and Frenkel defect. [May 2012, March 2008, 2011]
Schottky defect arises due to the missing of an equal number of cations and anions from their lattice sites. The density of the substance decreases.
Eg., NaCI, KCI, AgBr
Frenkel defect arises when the cation occupies the interstitial voids from its lattice site. A density of the substance does not change,
Eg., ZnS, AgCI, AgBr.
Crystal defects give rise to certain special properties in the solids.
a. What is meant by Frenkel defect?
b. Explain the pink colour of LiCI when heated in the vapours of Li.
c. Why does LiCI not exhibit Frenkel defect? [March 2011]
a. Frenkel defect arises due to the dislocation of a cation from its normal site to an interstitial site.
b. This is due to metal excess defect due to anionic vacancies. When LiCI is heated in vapours of Li, the Cl’ ions diffuse to the surface of the crystal creating vacant sites. Instead, the & electrons diffuse into the crystal and occupy these anionic sites, forming F-centres. These electrons absorb energy from white light and show pink colour.
c. Frenkel defect is shown by crystals with a large difference in size between the anion and cation. In LiCI, the cation and anion have comparable (similar) size. So it will not exhibit Frenkel defect.
When pure NaCI crystal Is heated In an atmosphere of sodium vapour ¡t turns yellow. Give a reason? KCI shows violet colour when heated in the presence of LI vapour- Why? (Say-201 2, March-2009J
This is due to the formation of F-centre. F-centres are formed when electrons are trapped in anionic vacancies. These trapped electrons are responsible for the colour of the crystal.
ClassIfy the following crystals Into those showing Schottky defects and Frenkel defects. NaCI, AgCl, CsCl, CdCl2. [March-2010]
Schottky defect: NaCI. CsCI
Frenkel defect: AgCI, CdCI2
Schematic alignment of magnetic moments of ferromagnetic, anti-ferromagnetic and ferrimagnetic substances are given below. Identify each of them.
Name a crystal showing both Schottky and Frenkel defect. [March2010]
NaCI shows Schottky defect and AgCI shows mainly Frenkel defect. Do you agree with this statement? Give reason. [Feb 2009, Mar 2009, 2010]
Yes, Schottky defect is shown by ionic substances in which the cation and anion are of almost similar sizes,
Frenkel defect is shown by ionic substances in which there is a large difference in the size of ions,
List out any four points of difference between crystalline and amorphous solids. [Say2010]
|Crystalline solids||Amorphous solids|
|Definite shape||Irregular shape|
|Have a sharp melting point||Do not have a sharp melting point|
|Anisotropic||Isotropic in nature|
|Short-range order||Long range order|
|Pseudo solids or supercooled||True solids|
|Undergoes irregular liquids cleavages||Can be cleaved along definite planes|
A set of solid substances are given below. Cs, SiC, Iodine, glass, KNO3 and Dry ice.
Classify them into ionic, molecular, amorphous, covalent or metallic solids. [Say2009]
Ionic solids – KNO3
Molecular solids – Iodine, Dry ice
Amorphous solids – Glass
Covalent solids – SiC
Metallic solids – Cs
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