Saturday, March 22, 2014

Magnesium - Chemistry

Magnesium occupies sixth position in order of the abundance on earth.

Magnesium is greyish white metal.

Magnesium is the lightest metal used in industry and it has a density less than two thirds of aluminium. Magnesium is an important alloying metal.


Some of the alloys of magnesium containing more than 90% magnesium and 2 to 9% of Aluminium and 1% zinc are used in automobile engines, in aircrafts and in making balances.
Up to 5% magnesium is added to most commercial aluminium alloys (duralumin, magnalium) to improve its resistance to corrosion, mechanical properties and weldability.

Magnesium is used as a reducing agent in metallurgy for the production of metals such as Titanium (Ti), Zirconium (Zr) and Hf.

Magnesium power is used in fireworks.

It is part of alkyl magnesium halide (RMgX), the Grignard reagent and it is useful for making numer of organic compounds.

Magnesium hydroxide and magnesium carbonate are used in making toothpastes.

Magnesium hydroxide (milk of magnesia) is used as an antacid. It neutralises excess of acid in stomach and thus it is used as medicine.

Ores of Magnesium

1. Carnallite
2. Magnesite
3. Dolomite
4. Epsom salt or epsomite
5. Langbeinite
6. Asbestos

Extraction of Magnesium from Its Ores

Magnesium is finally extracted by the electrolysis of its molten anhydrous salts.

From Magnesite
The ore MgCO3 is calcined to form the oxide MgO.
The oxide is mixed with carbon and heated in a current of Cl2 gas to form magnesium chloride.
Magnesium chloride is subjected to electrolysis.

Electrolysis of Magnesium chloride

Magnesium chloride is with a mixture of sodium chloride and calcium chloride and heated to 973 K - 1023 K. The mixture melts at this temperature and the electrolysis in carried out in an iron vessel which serves as the cathode.  A graphite rod serves as anode. During the electrolysis an inert gas such as coal gas is passed through the cell to check the oxidation of magnesium. At cathode magnesium will emerge in molten state and at anode chlorine gas will be released. The liquid magnesium (m.p. 924K) is removed from time to time from the top of the vessel.

Magnesium is a s-Block element.

Saturday, April 20, 2013

JEE (Advanced) 2013 Chemistry Syllabus

Physical Chemistry

General topics: Concept of atoms and
molecules; Dalton’s atomic theory; Mole
concept; Chemical formulae; Balanced
chemical equations; Calculations (based on
mole concept) involving common oxidation reduction, neutralisation, and displacement
reactions; Concentration in terms of mole
fraction, molarity, molality and normality.

Gaseous and liquid states: Absolute scale of
temperature, ideal gas equation; Deviation
from ideality, van der Waals equation; Kinetic
theory of gases; Average, root mean square
and most probable velocities and their relation
with temperature; Law of partial pressures;
Vapour pressure; Diffusion of gases.
Atomic structure and chemical bonding:
Bohr model, spectrum of hydrogen atom,
quantum numbers; Wave-particle duality, de
Broglie hypothesis; Uncertainty principle;
Qualitative quantum mechanical picture of
hydrogen atom, shapes of s, p and d orbitals;
Electronic configurations of elements (up to
atomic number 36); Aufbau principle; Pauli’s
exclusion principle and Hund’s rule; Orbital
overlap and covalent bond; Hybridisation
(involving s, p and d orbitals only); Orbital
energy diagrams for homonuclear diatomic
species; Hydrogen bond; Polarity in
molecules, dipole moment (qualitative aspects
only); VSEPR model and shapes of molecules
(linear, angular, triangular, square planar,
pyramidal, square pyramidal, trigonal
bipyramidal, tetrahedral and octahedral).
Energetics: First law of thermodynamics;
Internal energy, work and heat, pressurevolume work; Enthalpy, Hess’s law; Heat of
reaction, fusion and vapourization; Second law
of thermodynamics; Entropy; Free energy;
Criterion of spontaneity.

Chemical equilibrium: Law of mass action;
Equilibrium constant, Le Chatelier’s principle
(effect of concentration, temperature and
pressure); Significance of ΔG and ΔGo in
chemical equilibrium; Solubility product,
common ion effect, pH and buffer solutions;
Acids and bases (Bronsted and Lewis
concepts); Hydrolysis of salts.

Electrochemistry: Electrochemical cells and
cell reactions; Standard electrode potentials;
Nernst equation and its relation to ΔG;
Electrochemical series, emf of galvanic cells;
Faraday’s laws of electrolysis; Electrolytic
conductance, specific, equivalent and molar
conductivity, Kohlrausch’s law; Concentration
Chemical kinetics: Rates of chemical
reactions; Order of reactions; Rate constant;
First order reactions; Temperature dependence
of rate constant (Arrhenius equation).
Solid state: Classification of solids, crystalline
state, seven crystal systems (cell parameters
a, b, c,α,β,γ ), close packed structure of solids
(cubic), packing in fcc, bcc and hcp lattices;
Nearest neighbours, ionic radii, simple ionic
compounds, point defects.

Solutions: Raoult’s law; Molecular weight
determination from lowering of vapour
pressure, elevation of boiling point and
depression of freezing point.

Surface chemistry: Elementary concepts of
adsorption (excluding adsorption isotherms);
Colloids: types, methods of preparation and
general properties; Elementary ideas of
emulsions, surfactants and micelles (only
definitions and examples).

Nuclear chemistry: Radioactivity: isotopes
and isobars; Properties of α,β andγ rays;
Kinetics of radioactive decay (decay series
excluded), carbon dating; Stability of nuclei
with respect to proton-neutron ratio; Brief
discussion on fission and fusion reactions.

Inorganic Chemistry

Isolation/preparation and properties of the
following non-metals: Boron, silicon,
nitrogen, phosphorus, oxygen, sulphur and
halogens; Properties of allotropes of carbon
(only diamond and graphite), phosphorus and

Preparation and properties of the following
compounds: Oxides, peroxides, hydroxides,
carbonates, bicarbonates, chlorides and
sulphates of sodium, potassium, magnesium
and calcium; Boron: diborane, b
and calcium; Boron: diborane, boric acid and
borax; Aluminium: alumina, aluminium chloride
and alums; Carbon: oxides and oxyacid
(carbonic acid); Silicon: silicones, silicates and
silicon carbide; Nitrogen: oxides, oxyacids and
ammonia; Phosphorus: oxides, oxyacids
(phosphorus acid, phosphoric acid) and
phosphine; Oxygen: ozone and hydrogen
peroxide; Sulphur: hydrogen sulphide, oxides,
sulphurous acid, sulphuric acid and sodium
thiosulphate; Halogens: hydrohalic acids,
oxides and oxyacids of chlorine, bleaching
powder; Xenon fluorides.

Transition elements (3d series): Definition,
general characteristics, oxidation states and
their stabilities, colour (excluding the details of
electronic transitions) and calculation of spinonly magnetic moment; Coordination
compounds: nomenclature of mononuclear
coordination compounds, cis-trans and
ionisation isomerisms, hybridization and
geometries of mononuclear coordination
compounds (linear, tetrahedral, square planar
and octahedral).

Preparation and properties of the following
compounds: Oxides and chlorides of tin and
lead; Oxides, chlorides and sulphates of Fe2+,
Cu2+ and Zn2+; Potassium permanganate,
potassium dichromate, silver oxide, silver
nitrate, silver thiosulphate.

Ores and minerals: Commonly occurring ores
and minerals of iron, copper, tin, lead,
magnesium, aluminium, zinc and silver.

Extractive metallurgy: Chemical principles
and reactions only (industrial details excluded);
Carbon reduction method (iron and tin); Self
reduction method (copper and lead);
Electrolytic reduction method (magnesium and
aluminium); Cyanide process (silver and gold).
Principles of qualitative analysis: Groups I to
V (only Ag+, Hg2+, Cu2+, Pb2+, Bi3+, Fe3+,
Cr3+, Al3+, Ca2+, Ba2+, Zn2+, Mn2+ and
Mg2+); Nitrate, halides (excluding fluoride),
sulphate and sulphide.

Organic Chemistry

Concepts: Hybridisation of carbon; Sigma and
pi-bonds; Shapes of simple organic molecules;
Structural and geometrical isomerism; Optical
isomerism of compounds containing up to two
asymmetric centres, (R,S and E,Z
nomenclature excluded); IUPAC nomenclature
of simple organic compounds (only
hydrocarbons, mono-functional and bifunctional compounds); Conformations of
ethane and butane (Newman projections);
Resonance and hyperconjugation; Keto-enol
tautomerism; Determination of empirical and
molecular formulae of simple compounds (only
combustion method); Hydrogen bonds:
definition and their effects on physical
properties of alcohols and carboxylic acids;
Inductive and resonance effects on acidity and
basicity of organic acids and bases; Polarity
and inductive effects in alkyl halides; Reactive
intermediates produced during homolytic and
heterolytic bond cleavage; Formation,
structure and stability of carbocations,
carbanions and free radicals.

Preparation, properties and reactions of
alkanes: Homologous series, physical
properties of alkanes (melting points, boiling
points and density); Combustion and
halogenation of alkanes; Preparation of
alkanes by Wurtz reaction and decarboxylation

Preparation, properties and reactions of
alkenes and alkynes: Physical properties of
alkenes and alkynes (boiling points, density
and dipole moments); Acidity of alkynes; Acid
catalysed hydration of alkenes and alkynes
(excluding the stereochemistry of addition and
elimination); Reactions of alkenes with KMnO4
and ozone; Reduction of alkenes and alkynes;
Preparation of alkenes and alkynes by
elimination reactions; Electrophilic addition
reactions of alkenes with X2, HX, HOX and
O (X=halogen); Addition reactions of
alkynes; Metal acetylides.

Reactions of benzene: Structure and
aromaticity; Electrophilic substitution reactions:
halogenation, nitration, sulphonation, FriedelCrafts alkylation and acylation; Effect of o-, mand p-directing groups in monosubstituted

Phenols: Acidity, electrophilic substitution
reactions (halogenation, nitration and
sulphonation); Reimer-Tiemann reaction, Kolbe
Characteristic reactions of the following
(including those mentioned above): Alkyl
halides: rearrangement reactions of alkyl
carbocation, Grignard reactions, nucleophilic
substitution reactions; Alcohols: esterification,
dehydration and oxidation, reaction with
sodium, phosphorus halides,
ZnCl2/concentrated HCl, conversion of
alcohols into aldehydes and ketones; Ethers:
Preparation by Williamson’s Synthesis;

Aldehydes and Ketones: oxidation, reduction,
oxime and hydrazone formation; Aldol
condensation, Perkin reaction; Cannizzaro
reaction; Haloform reaction and nucleophilic
addition reactions (Grignard addition);
Carboxylic acids: formation of esters, acid
chlorides and amides, ester hydrolysis;

Amines: basicity of substituted anilines and
aliphatic amines, preparation from nitro
compounds, reaction with nitrous acid, azo
coupling reaction of diazonium salts of
aromatic amines, Sandmeyer and related
reactions of diazonium salts; carbylamine
reaction; Haloarenes: nucleophilic aromatic
substitution in haloarenes and substituted
haloarenes (excluding Benzyne mechanism
and Cine substitution).

Carbohydrates: Classification; mono- and disaccharides (glucose and sucrose); Oxidation,
reduction, glycoside formation and hydrolysis
of sucrose.

Amino acids and peptides: General structure
(only primary structure for peptides) and
physical properties.
Properties and uses of some important
polymers: Natural rubber, cellulose, nylon,
teflon and PVC.

Practical organic chemistry: Detection of
elements (N, S, halogens); Detection and
identification of the following functional groups:
hydroxyl (alcoholic and phenolic), carbonyl
(aldehyde and ketone), carboxyl, amino and
nitro; Chemical methods of separation of
mono-functional organic compounds from
binary mixtures.

Sunday, September 30, 2012

IIT JEE Chemistry Concepts Revision Materials

IIT JEE Chemistry Concepts Revision Materials

IIT JEE Chemistry Concepts Revision Materials

Revision points in various chapters of chemistry at 11 and 12 standards (Classes) and especially for IIT JEE.
Revision points for revision at the end of study of a chapter as well as for periodic and final revisions. These revision points will be scheduled as a plan for revision for JEE 2010 and JEE 2011 during (January 2010 to April 2010)
Detailed topicwise revision points 
    JEE Revision - Hund's rule     
    Revision - Hess's law   

Saturday, July 21, 2012

Stereochemistry - Introduction

Stereochemistry is the study of the orientation in space of the atoms of a molecule.  There are molecules with the same molecular formula and structure but with different orientations of atoms in space. There are significant number cases, in which it happens.

It is found that there are molecules, in which we find  two different  molecules are mirror-images of each other, but they will not super-impose and remain as two separate chemical entities.  They are known as enantiomers.

The physical and chemical properties of the enantiomers are the same in a symmetrical environment, but differ if there is asymmetry in the environment (e.g. a biological system).  Enantiomers also differ in the direction that they rotate plane-polarized light.  Both enantiomers will rotate the plane of the light to the same extent, but in opposite directions.  Such molecules are said to be optically active.

Concepts in Stereochemistry

Enantiomers: "A species with a non-superimposable mirror image."  An example of a pair of enantiomers is lactic acid.

Racemic mixture, or racemate: A racemic mixture, or racemate is a mixture of exactly equal quantities of both enantiomers, so that it does not rotate plane-polarized light in either direction (as the effects of both enantiomers cancel out.)

More information

Chemistry Knowledge History - January

Chemistry Knowledge History - February

Chemistry Knowledge History - March