Compendium ClassXIIChemistry

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Compendium/Chemistry/Class XII 1 © 2010 Vidyamandir Classes Dear Students, Vidyamandir Classes academic team knows that you are rigourously studying to cover the entire prescribed syllabus. As the Final Exams approach, this is the time when you need to revisit the concepts you have learned. At this time, you have to be very focused and directed in your approach. To make your learning process precise, effective and enjoyable, we at Vidyamandir Classes conceptualized the compendium series, strategically designed to help you in scoring high grades in examination. The Compendium is primarily intended to present the concepts of chapter in a concise manner. All key definitions, diagrams and formulae have been integrated for a quick revision of the chapter. To help you to easily master complicated concepts, definitions, diagrams and formulae, we have added interesting tips, mnemonics, maps and matrices. Let us take a look at the elements of the Compendium and how to use them. Knowing these features will make it easier for you to assimilate complex information. Icon Description How it can help you Concept map To directly recapitulate main concepts of the chapter. Drawing Tips Drawing Tips To help you draw and remember diagrams, we have thoughtfully developed some mnemonics to help you to memorise information Compare Contrast Matrix To help you in comparing different concepts Memory Tips To make your learning process effective, easy tips have been provided. In this compendium, we have also incorporated: CBSE Blue Print: Type of questions asked and the weightage of different forms of questions. Analysis of Previous Years CBSE questions: The topic wise analysis of previous years question along with the marks allocated. We are confident that this Compendium will prove very helpful in achieving excellent result in your exams. All the very best for your exams! Vidyamandir Classes Academic Team ABOUT THE COMPENDIUM

Transcript of Compendium ClassXIIChemistry

Page 1: Compendium ClassXIIChemistry

Compendium/Chemistry/Class XII 1 © 2010 Vidyamandir Classes

Dear Students,Vidyamandir Classes academic team knows that you are rigourously studying to cover the entire prescribedsyllabus. As the Final Exams approach, this is the time when you need to revisit the concepts you havelearned. At this time, you have to be very focused and directed in your approach.To make your learning process precise, effective and enjoyable, we at Vidyamandir Classes conceptualizedthe compendium series, strategically designed to help you in scoring high grades in examination. TheCompendium is primarily intended to present the concepts of chapter in a concise manner. All key definitions,diagrams and formulae have been integrated for a quick revision of the chapter.To help you to easily master complicated concepts, definitions, diagrams and formulae, we have addedinteresting tips, mnemonics, maps and matrices. Let us take a look at the elements of the Compendium andhow to use them.Knowing these features will make it easier for you to assimilate complex information.

Icon Description How it can help you

Concept map To directly recapitulate main concepts of the

chapter.

Drawing Tips

Drawing Tips

To help you draw and remember diagrams, we have thoughtfully developed some mnemonics to help you to memorise information

Compare Contrast Matrix To help you in comparing different concepts

Memory Tips To make your learning process effective, easy

tips have been provided.

In this compendium, we have also incorporated:• CBSE Blue Print: Type of questions asked and the weightage of different forms of questions.• Analysis of Previous Years CBSE questions: The topic wise analysis of previous years question along

with the marks allocated.• We are confident that this Compendium will prove very helpful in achieving excellent result in your

exams.

All the very best for your exams!Vidyamandir Classes Academic Team

ABOUT THE COMPENDIUM

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Compendium/Chemistry/Class XII 2 © 2010 Vidyamandir Classes

The Solid State

Matter exists in nature in four states namely solid, liquid, gas and plasma. All these statesdiffer from each other in attractive forces, and arrangement of particles. This chapter looks atsolid state in detail.

Solids are of two types as given in the following table with their properties:

About The Solid State

Property Crystalline Solids Amorphous Solids

1. Shape Have definite characteristic geometrical shape

Irregular shape

2. Melting point

Have sharp and characteristic temperature

Soften over a range of temperature

3. Cleavage property

On cutting with a sharp edge tool, these cut into two pieces having smooth surfaces and plain

On cutting with a sharp edge tool, these cut into two pieces with irregular surfaces

4. Anisotropy Isotropic in nature Anisotropic in nature

5. Nature True solids Pseudo solids or supercooled liquids

6. Order in arrangement of constituent particles

Long range order Short range order

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Molecular solids Type of solid Non polar Polar Hydrogen

bonded

Ionic solids Metallic solids

Covalent or network solids

Examples Ar, CCl4 HCl, SO2, HBr

H2O (ice)

NaCl, CsCl, MgO, ZnS, CaF2

Fe, Cu, Ag, Mg

SiO2 (quartz), SiC, C (diamond), AlN, C(graphite)

Constituent particles

Molecules Molecules Molecules Ions Positive ions in sea of delocalized

Atoms

Bonding forces Weak dispersion forces

Dipole-dipole interaction

Hydrogen bonds

Coulombic Metallic bonding

Covalent bonding

Physical nature Soft Soft Hard Hard but brittle

Hard but malleable and ductile

Hard, graphite is soft

Melting point Very low Low Low High Fairly high Very high Electrical conductivity

Insulator Insulator Insulator Insulator in solid state but conductors in molten state or aqueous solutions

Conductors Insulators Graphite (exception) is conductor

Crystalline solids can be further classified into four categories.

Crystal LatticesThe constituent particles (atoms, ions or molecules) of a crystal are arranged in a definite andregular order in space. The relative positions of such particles in a crystal are shown by points.The arrangement of these points in a crystal is called space lattice. The seven crystal systemsform the 14 possible Bravais lattices listed in the following table:

Crystal System Types of Lattices

Cubic Simple, Face centred, Body centred

Tetragonal Simple, Body centred

Orthorhombic Simple, Face centred, Body centred, End Centred

Monoclinic Simple, End Centred

Rhombohedra Simple

Triclinic Simple

Hexagonal Simple

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The seven crystal systems form the following Bravais lattices according to the arrangement ofthe points in the different unit cells involved.

Figures of 14 Bravais lattices associated with the seven crystal systems are:

Crystal system Possible variation

Axial distances or edge lengths

Axial angles Examples

Cubic

Primitive, Body-centred, Face-centred

a = b = c

α = β = γ = 90°

NaCl, KCl, Diamond, Zinc blende (ZnS), Cu, Ag

Tetragonal

Primitive, Body-centred

a = b c

α = β = γ = 90°

White tin, SnO2, TiO2, CaSO4

Orthorhombic

Primitive, Body-centred, Face-centred, End-centered

a b c

α = β = γ = 90°

Rhombic sulphur, KNO3, K2SO4, BaSO4, PbCO3

Hexagonal Primitive a = b c α = β = 90°, γ = 120° Graphite, ZnO, CdS, PbI2

Rhombohedral or Trigonal

Primitive a = b = c α = β = γ 90° Calcite (CaCO3), quartz NaNO3, HgS (Cinnabar)

Monoclinic

Primitive, End-centered

a b c

α = γ = 90°, β 120°,

Monoclinic sulphur, Na2SO4 .10H2O

Triclinic Primitive a b c α β γ 90° CuSO4.5H2O, K2Cr2O7, H3BO3

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CENTRED UNIT CELLS

Atoms are present at eight corners(one atom shared between eightcubes) and one (not shared withany) atom is present at the centreof the cube.

Atoms are present at eight corners(one atom shared between eightcubes) and six atoms (each sharedbetween two cubes) present on thesix faces of the cube.

Body-centred unit cell

No. of atoms in unit cell1 8+1 28

Face-centred unit cell

No. of atoms in unit cell 1 1= 8+6 48 2

End-centred unit cells

CLOSE PACKED STRUCTURESIn solids the constituent particles are close-packed, leaving minimum vacant space. Closepackings are of following types:(i) Close Packing in One Dimension: the spheres representing particles touch each other in a

row, the coordination number is 2.

(ii) Close Packing in Two Dimensions:Square close packing: Can be generated by placing together the rows of close packedspheres (Arrangement 1).Hexagonal close packing: Generated by placing the second row on the depression betweenthe spheres of first row (Arrangement II).

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Voids: The empty spacesbetween atoms in a crystal arecalled voids. Voids are of threetypes: tetrahedral, octahedraland trigonal voids.

(iii) Close Packing in Three Dimensions:

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IMPERFECTIONS IN SOLIDS: CRYSTAL DEFECTS

Types of Defects Diagram Examples

Vacancy defect

Some lattices are vacant

Point defects

Stoichiometric defects

Interstitial defect

Constituent particles occupy an interstitial site

Calculations involving unit celldimensions

Density of anunitcellMassof unitcell

Volumeof unit cellzMor d 3a NA

where, z = number of atoms inunit cell

M = Molar massNA = Avogadro constanta3 = Volume of unit cell

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Frenkel defect, also called dislocation defect

A vacancy defect at original site and interstitial defect at new location,

ZnS, AgCl, AgBr, AgI

Stoichiometric defects

Schottky defect

This defect has equal number of cations and anions

NaCL, CsCl, KCl, AgBr

Impurity defects Impurity occupies the sites of a crystal

SrCl2 in NaCl, solid solution of CdCl2 and AgCl

Metal excess defect

Due to the presence of extra cations at interstitial sites

ZnO

Point defects

Non stoichiometric defects

Metal deficiency defect

Have less amount of metal compared to stoichiometric proportion

FeO which is mostly found with a composition of Fe0.95O

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ANALYSIS OF CBSE QUESTIONS (2004-08)

CONCEPTS YEAR(S)

Crystal structure, formula of compound Close packed structures Defects in crystals Semiconductors Magnetic properties Numerical on unit cell dimensions

2008, 2006, 2005 2007 2007, 2006, 2004 2007 2007 2008, 2007, 2006, 2005, 2004

CBSE BLUEPRINT

Types of questions Very short answer (1 mark)

Short answer I (2 marks)

Short answer II (3 marks)

Total marks

Option I 1 – 1 1 + 3 = 4

Option II – 2 – 2 2 = 4

Tips to answer

Formula of a compound Check the type of lattice (ccp, hcp, etc.), find the number of voids and occupancy of the elements of the compound in lattice and voids. Find the ratio of two, e.g., A:B = 4:3 gives the formula A4B3

Coordination number Find the type of packing, then the number of closest neighbours

Doping Indicate the type of element with which silicon, germanium are to be doped, e.g. group 15 element gives n-type (electron rich) whereas group 13 element gives p-type (electron deficient) semiconductors

Number of atoms in unit cell Check that how many atoms are shared between the unit cells in vicinity and calculate accordingly

Atomic radius, density, number of atoms etc.

Can be calculated using formula

3A

Z×MDensity of the unitcell = a N

Number of tetrahedral voids Twice the number of atoms

Number of octahedral voids Number of atoms

Number of vacancies on adding ions

Number of corresponding ions added