( ii ) At STP or NTP ( T = 273 K and p = 1 atm 22.4 L of each gas has 6.023 x 10 23 molecules .
( iii ) One mole of any gas at STP occupies 22.4 L of volume .
Standard or Perfect Gas Equation
Gases which obey all gas laws in all conditions of pressure and temperature are called perfect gases .
Equation of perfect gas pV = nRT
where p = pressure , V = volume , T = absolute temperature , R = universal gas constant and n = number of moles of a gas .
Universal gas constant R = 8.31 J mol -1 K -1 . Real Gases Real gases deviate slightly from ideal gas laws because
Real gas molecules attract one another . Real gas molecules occupy a finite volume .
Real or Van der Waal ’ s Gas Equation ( p + a / V 2 ) ( V – b ) = RT where a and b are called van der Waals ’ constants .
Pressure due to an ideal gas is given by p = ( 1 / 3 ).( mn / V ). c 2 = 1 / 3 ρ c 2
For one mole of an ideal gas P = ( 1 / 3 ).( M / V ). c 2
where , m = mass of one molecule , n = number of molecules , V = volume of gas , c = ( c1 2 + c2 2 + … + cn 2 ) / n allde root mean square ( rrns ) velocity of the gas molecules and M = molecular weight of the gas . If p is the pressure of the gas and E is the kinetic energy per unit volume is E , then
p = ( 2 / 3 ). E