## Saturday, January 19, 2008

### IIT JEE Ch.2. GASEOUS, LIQUID AND SOLID STATES - Core Points for Revision

JEE syllabus

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.

Solid state:
Classification of solids,
crystalline state,
seven crystal systems (cell parameters a, b, c, alpha, beta, gamma),
close packed structure of solids (cubic), packing in fcc, bcc and hcp lattices; Nearest neighbours,
simple ionic compounds,
point defects.

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pV = nRT

Vander Waals correction

[p + n²a/V²] [V-nb] = nRT

Graham's Law of Diffusion: The rate of diffusion of a gas is inversely proportional to the square root of its density or molar mass.

Liquids

Vapour pressure
Teh vapour pressure of a liquid may be defined as the pressure of vapour in equilibrium with the liquid. It increases with increase in temperature.

Solid State

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

Classification crystalline solids based on bond type:

Molecular
ionic
covalent
metallic

a space lattice represents a three dimensional translational repetition of the centres of gravity of the units of pattern in the crystals by means of points. These points are called lattice points.

Unit cell: A unit cell represents a parallelopiped obtained by connecting the lattice point such that each parallelopiped contains a complete unit of pattern of the crystal. By stacking of the parallelopipeds the entire crystal structure can be generated.

Parameters to describe a unit cell: Six parameters are required. These are the three basic vectors along three crystallographic axes(a,b, and c) and three angles between the crystallographic axes(α,β,γ).

Based on the presence of certain rotation axes in the unit cell, crystals can be classifed into seven categories

Triclinic
Monoclinic
Orthoclinic
Trigonal
Tetragonal
Hexagonal

packing of crystals; Body centred cubic(bcc), Hexagonal closed packed 9hcp) and cubical close packed (ccp)

Point defects: Schottsky defects, Frenkel defects