Thursday, 9 July 2009

Ideal Gas Law

Ideal Gas Law:
Macroscopic properties of matter are governed by the Ideal Gas Law of chemistry.
An ideal gas is a gas that conforms, in physical behavior, to a particular, idealized
relation between pressure, volume, and temperature. The ideal gas law states that for a
specified quantity of gas, the product of the volume, V, and pressure, P, is
proportional to the absolute temperature T; i.e., in equation form, PV = kT, in which k
is a constant. Such a relation for a substance is called its equation of state and is
sufficient to describe its gross behavior.
Although no gas is perfectly described by the above law, the behavior of real gases is
described quite closely by the ideal gas law at sufficiently high temperatures and low
pressures (such as air pressure at sea level), when relatively large distances between
molecules and their high speeds overcome any interaction. A gas does not obey the
equation when conditions are such that the gas, or any of the component gases in a
mixture, is near its triple point.
The ideal gas law can be derived from the kinetic theory of gases and relies on the
assumptions that (1) the gas consists of a large number of molecules, which are in
random motion and obey Newton's deterministic laws of motion; (2) the volume of the
molecules is negligibly small compared to the volume occupied by the gas; and (3) no
forces act on the molecules except during elastic collisions of negligible duration.

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