( 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