Saturday, July 27, 2019

Chemistry - Open Text Book




https://cnx.org/contents/havxkyvS@12.1:uXg0kUa-@5/Introduction





Preface
1 Essential Ideas
Introduction
1.1 Chemistry in Context   Chemistry in Context
1.2 Phases and Classification of Matter
1.3 Physical and Chemical Properties
1.4 Measurements
1.5 Measurement Uncertainty, Accuracy, and Precision
1.6 Mathematical Treatment of Measurement Results
2 Atoms, Molecules, and Ions
Introduction
2.1 Early Ideas in Atomic Theory
2.2 Evolution of Atomic Theory
2.3 Atomic Structure and Symbolism
2.4 Chemical Formulas
2.5 The Periodic Table
2.6 Molecular and Ionic Compounds
2.7 Chemical Nomenclature
3 Composition of Substances and Solutions
Introduction
3.1 Formula Mass and the Mole Concept
3.2 Determining Empirical and Molecular Formulas
3.3 Molarity
3.4 Other Units for Solution Concentrations
4 Stoichiometry of Chemical Reactions
Introduction
4.1 Writing and Balancing Chemical Equations
4.2 Classifying Chemical Reactions
4.3 Reaction Stoichiometry
4.4 Reaction Yields
4.5 Quantitative Chemical Analysis
5 Thermochemistry
Introduction
5.1 Energy Basics
5.2 Calorimetry
5.3 Enthalpy
6 Electronic Structure and Periodic Properties of Elements
Introduction
6.1 Electromagnetic Energy
6.2 The Bohr Model
6.3 Development of Quantum Theory
6.4 Electronic Structure of Atoms (Electron Configurations)
6.5 Periodic Variations in Element Properties
7 Chemical Bonding and Molecular Geometry
Introduction
7.1 Ionic Bonding
7.2 Covalent Bonding
7.3 Lewis Symbols and Structures
7.4 Formal Charges and Resonance
7.5 Strengths of Ionic and Covalent Bonds
7.6 Molecular Structure and Polarity
8 Advanced Theories of Covalent Bonding
Introduction
8.1 Valence Bond Theory
8.2 Hybrid Atomic Orbitals
8.3 Multiple Bonds
8.4 Molecular Orbital Theory
9 Gases
Introduction
9.1 Gas Pressure
9.2 Relating Pressure, Volume, Amount, and Temperature: The Ideal Gas Law
9.3 Stoichiometry of Gaseous Substances, Mixtures, and Reactions
9.4 Effusion and Diffusion of Gases
9.5 The Kinetic-Molecular Theory
9.6 Non-Ideal Gas Behavior
10 Liquids and Solids
Introduction
10.1 Intermolecular Forces
10.2 Properties of Liquids
10.3 Phase Transitions
10.4 Phase Diagrams
10.5 The Solid State of Matter
10.6 Lattice Structures in Crystalline Solids
11 Solutions and Colloids
Introduction
11.1 The Dissolution Process
11.2 Electrolytes
11.3 Solubility
11.4 Colligative Properties
11.5 Colloids
12 Kinetics
Introduction
12.1 Chemical Reaction Rates
12.2 Factors Affecting Reaction Rates
12.3 Rate Laws
12.4 Integrated Rate Laws
12.5 Collision Theory
12.6 Reaction Mechanisms
12.7 Catalysis
13 Fundamental Equilibrium Concepts
Introduction
13.1 Chemical Equilibria
13.2 Equilibrium Constants
13.3 Shifting Equilibria: Le Châtelier’s Principle
13.4 Equilibrium Calculations
14 Acid-Base Equilibria
Introduction
14.1 Brønsted-Lowry Acids and Bases
14.2 pH and pOH
14.3 Relative Strengths of Acids and Bases
14.4 Hydrolysis of Salt Solutions
14.5 Polyprotic Acids
14.6 Buffers
14.7 Acid-Base Titrations
15 Equilibria of Other Reaction Classes
Introduction
15.1 Precipitation and Dissolution
15.2 Lewis Acids and Bases
15.3 Multiple Equilibria
16 Thermodynamics
Introduction
16.1 Spontaneity
16.2 Entropy
16.3 The Second and Third Laws of Thermodynamics
16.4 Free Energy
17 Electrochemistry
Introduction
17.1 Balancing Oxidation-Reduction Reactions
17.2 Galvanic Cells
17.3 Standard Reduction Potentials
17.4 The Nernst Equation
17.5 Batteries and Fuel Cells
17.6 Corrosion
17.7 Electrolysis
18 Representative Metals, Metalloids, and Nonmetals
Introduction
18.1 Periodicity
18.2 Occurrence and Preparation of the Representative Metals
18.3 Structure and General Properties of the Metalloids
18.4 Structure and General Properties of the Nonmetals
18.5 Occurrence, Preparation, and Compounds of Hydrogen
18.6 Occurrence, Preparation, and Properties of Carbonates
18.7 Occurrence, Preparation, and Properties of Nitrogen
18.8 Occurrence, Preparation, and Properties of Phosphorus
18.9 Occurrence, Preparation, and Compounds of Oxygen
18.10 Occurrence, Preparation, and Properties of Sulfur
18.11 Occurrence, Preparation, and Properties of Halogens
18.12 Occurrence, Preparation, and Properties of the Noble Gases
19 Transition Metals and Coordination Chemistry
Introduction
19.1 Occurrence, Preparation, and Properties of Transition Metals and Their Compounds
19.2 Coordination Chemistry of Transition Metals
19.3 Spectroscopic and Magnetic Properties of Coordination Compounds
20 Organic Chemistry
Introduction
20.1 Hydrocarbons
20.2 Alcohols and Ethers
20.3 Aldehydes, Ketones, Carboxylic Acids, and Esters
20.4 Amines and Amides
21 Nuclear Chemistry
Introduction
21.1 Nuclear Structure and Stability
21.2 Nuclear Equations
21.3 Radioactive Decay
21.4 Transmutation and Nuclear Energy
21.5 Uses of Radioisotopes
21.6 Biological Effects of Radiation
The Periodic Table
Essential Mathematics
Units and Conversion Factors
Fundamental Physical Constants
Water Properties
Composition of Commercial Acids and Bases
Standard Thermodynamic Properties for Selected Substances
Ionization Constants of Weak Acids
Ionization Constants of Weak Bases
Solubility Products
Formation Constants for Complex Ions
Standard Electrode (Half-Cell) Potentials
Half-Lives for Several Radioactive Isotopes


The Scientific Method

Chemistry is a science based on observation and experimentation. Doing chemistry involves attempting to answer questions and explain observations in terms of the laws and theories of chemistry, using procedures that are accepted by the scientific community. There is no single route to answering a question or explaining an observation, but there is an aspect common to every approach: Each uses knowledge based on experiments that can be reproduced to verify the results. Some routes involve a hypothesis, a tentative explanation of observations that acts as a guide for gathering and checking information. We test a hypothesis by experimentation, calculation, and/or comparison with the experiments of others and then refine it as needed.

Some hypotheses are attempts to explain the behavior that is summarized in laws. The laws of science summarize a vast number of experimental observations, and describe or predict some facet of the natural world. If such a hypothesis turns out to be capable of explaining a large body of experimental data, it can reach the status of a theory. Scientific theories are well-substantiated, comprehensive, testable explanations of particular aspects of nature. Theories are accepted because they provide satisfactory explanations, but they can be modified if new data become available. The path of discovery that leads from question and observation to law or hypothesis to theory, combined with experimental verification of the hypothesis and any necessary modification of the theory, is called the scientific method.
 Chemistry in Context

Thursday, July 25, 2019

2. Solid State - JEE Main - Core Revision Points

Importance of  Core Revision Points: Core Revision Points are important because if you remember them strongly, many more points related to them will come out of your memory and help you to answer question and problems. Read them many times and make sure you remember them very strongly.


JEE Syllabus (2015)  on Solid State Topic


Solid State: Classification of solids: molecular, ionic, covalent and metallic solids, amorphous and crystalline solids (elementary idea); Unit cell and lattices, packing in solids (fcc, bcc and hcp lattices), voids,   Bragg’s Law and its applications; calculations involving unit cell parameters, imperfection in solids; Electrical, magnetic and dielectric properties.


Jauhar, CBSE XII class

Sections in the Chapter


2.1 Space Lattices and Unit Cell
2.2 Close Packing in Crystalline Solids
2.3 Interstitial Sites or Interstitial Voids
2.4 Types of Cubic Crystals and Number of Atoms per Unit Cell
2.5 Experimental Methods of Determining Crystal Structure: X Rays Diffraction
2.6 Coordination Number and Radius Ratio
2.7 Ionic Radii
2.8 Calculation of Density of a Crystal from its Structure
2.9 Structures of Ionic Compounds
2.10 Imperfections in solids
2.11 Properties of solids
2.12 Amorphous solids


Solid State - Revision Points



The main content covered in the chapter is about the formation of crystals in solids. Last section 2.12 is about amorphous solids which are not crystalline solids.


Solids can be broadly classified into two categories: crystalline and amorphous.


Crystalline solids


The outstanding features are its flat faces and share edges which in a well developed form are usually arranged symmetrically.  Therefore, there is a high degree of internal order throughout the crystal. There is a definite pattern constantly repeating in space that forms the crystal. This order in the crystal is known as long-range order.

Amorphous solids


Amorphous solids are not crystals and they do not have long range order but have short-range order. An ordered arrangement exists around some atoms, molecules or ions only up to short distances. The same order will not be found around other atoms or molecules in the solid at another place. In many was amorphous solids are more closely related to liquids and are therefore regarded as supercooled liquids with high viscosity.  Some crystalline materials can be converted into amorphous or glassy form by rapidly cooling the melt. Freezing the vapours also gives rise to amorphous solids.

Bonds Present in  Solids



Molecular bonds:  In these solids, the constituent particles are molecules. The molecules are held together by weak Van der Waals forces. Examples are iodine, ice and solid carbon dioxide.

Ionic bonds:  Ionic solids have positively and negatively charged ions which are arranged in crystal form and held together by strong electrostatic forces. Examples are salts like NaCl, NaNO3, LiF and Na2SO4 etc.

Covalent bonds:  In these solids, the constituent particles are atoms and they are held together by covalent bonds. Examples are diamond, silicon carbide, and silica.


Metallic bonds: In solids with metallic bonds, positive kernels are immersed in a sea of mobile electrons. The forces between the constituents, positive kernels and electrons form the metallic bonds. These bonds are present in metals like copper, nickel etc.

2.1 Space Lattice and Unit Cell


The crystalline solids have their constituent particles - molecules, ions or atoms at specific locations in a three dimensional space, the basic shape of which repeats many times to form the crystalline solid.  The arrangement of this infinite set of points at which the constituent particles of the solid exist is called space lattice.

Space Lattice


A space lattice is a regular arrangement of the  constituent particles of a crystalline solid in three dimensional space. These points are called lattice points.

Unit Cell


A unit cell is the smallest repeating unit in space lattice.



Parameters to describe a unit cell


Six parameters are required.  The unit cell is assumed to be formed of straightline in three axes.

These the three basic vectors along three crystallographic axes are termed (a,b, and c). Three angles are there between the crystallographic axes (α,β,γ). The angle α is between the edges b and c, The angle β is between edges c and a. The angle γ is between the edges b and a.


Seven Crystal Systems


Crystals can be classified into seven categories


Triclinic -  a is not equal to b  is not equal to - (α,β,γ) are different and not equal to 90 degrees

Monoclinic

Orthoclinic

Trigonal or Rhombohedral

Cubic

Tetragonal

Hexagonal


2.2   Close Packing in Crystalline Solids

In the formation of crystals, closed packing of the constituent particles takes place.



Square Pattern

To understand arrangement of the particles in a solid one can visualise four particles arranged as a square. In this one particle assumed as a sphere is above another particles and four such sphere form a square and the pattern is repeated. But this pattern is not the usual pattern because only 52.4% of the available space becomes occupied in this square pattern of packing.

Hexagonal Pattern

In hexagonal close packing of particles (assumed as spheres), the spheres in the second row are placed in the depressions between the spheres in the first row. (In earlier square pattern, a sphere is placed on another sphere. But now a sphere is placed in the depression between two spheres in  the row below. In this packing, 60.4% of space gets occupied. Hence this hexagonal close packing gives more close packing.

Co-ordination Number

The number of spheres which are touching a given sphere in packing arrangement is called co-ordination number. Thus in two dimensional representation coordination number is 4 in square arrangement and six in hexagonal arrangement.

Good web page for the above topics Lattice Structures in Crystalline Solids  https://opentextbc.ca/chemistry/chapter/10-6-lattice-structures-in-crystalline-solids/




2.3 Interstitial Sites or Interstitial Voids

In the packed structure of the crystalline solid, there are hollow spaces between particles. These holes are voids are called interstitial sites or interstitial voids. Two important interstitial sites are 1. Tetrahedral interstitial site.  (2) Octahedral interstitial site.


2.4 Types of Cubic Crystals and Number of Atoms per Unit Cell

There are three common types of cubic crystals.

1. Simple cubic
2. Body centred cubic
3. Face centred cubic or cubic close packing

2.5 Experimental Methods of Determining Crystal Structure: X Rays Diffraction


The structure of solid is studied by X-ray diffraction methods.

Bragg Equation:

n lamba = 2d sin theta

where d = distance between the planes of the constituent particles of the  crystal.
lamba = wave length of the x-ray used.
n =  1,2,3 etc.  standing for the serial order of the diffracted beam.


2.6 Coordination Number and Radius Ratio
2.7 Ionic Radii
2.8 Calculation of Density of a Crystal from its Structure
2.9 Structures of Ionic Compounds
2.10 Imperfections in solids
2.11 Properties of solids
2.12 Amorphous solids


close packed structure of solids (cubic), packing in fcc, bcc and hcp lattices;

packing of crystals;
Body centred cubic(bcc),
Hexagonal closed packed (hcp) and

cubical close packed (ccp)

Point defects: Schottsky defects, Frenkel defects


Practice questions

http://makoxmcqs.com/chemistry-mcqs-for-iit-jee-s-block-elements-mcq-practice-sheet/


See an Oxford Video on Crystal Structure
09. Geometry of Solids I: Crystal Structure in Real Space
http://podcasts.ox.ac.uk/09-geometry-solids-i-crystal-structure-real-space

Good Websites for Solid State Topic

Updated on 27 July 2019
6 June 2015
Originally published  22 May 2015