While various gases will differ in their behaviours due to small differences in intermolecular forces and molecular size, they still tend to behave much like one another; thus the concept of an ideal gas was created. An ideal gas is an imaginary gas which has no intermolecular forces and no molecular volume. Its properties closely approximate those of real gasses under most conditions.
Ideal Gas Law
When we describe an ideal gas we are intrestaed in four variables. These varables are listed below along with common conversions factors.
P, pressure ( 1 atm = 760 mm Hg) , ( 1 atm = 760 torr ) , ( 1 atm = 1x 10^5 Pa )
V , volume ( 1 L = 1000 mL ) , ( 1 L = 1000 cm ^3 ) , ( 1 m^3 = 1000 L ).
n , moles ( # moles = # grams /MW).
T , temparature. ( K = o C + 273 ), where K is the temparature expressed in Kelvin.
The relationship of the above variables is given in the ideal gas equation below:
PV = n RT
where P is in atm, V is in L, T is in Kelvin. R is the gas constant which is equal tp 0.082 L.atm/mol.K. ( When SI units are used R = 8.3 J/mol.K )
An ideal gas is de¯ned as a hypothetical substance that obeys the ideal gas equation of state. We will see later that all real gases behave more and more like an ideal gas as the pressure approaches zero. A pressure of only 1 atm is su±ciently close to zero to make this relation useful for most gases at this pressure.
Boyle's law states that a sample of gas at a constant temperature will have a volume which is inversely proportional to its pressure.
PV = k or P1V1 = P2V2
Charles's Law states that a sample of gas at a constant pressure will have a volume which is directly proportinal to its temparature.
V/T = k or V1/T1 = V2/T2