Question

How many oxygen molecules are in 22.4 liters of oxygen gas at 273 K and 101.3 kPa

Answer 1

This 273 K and 101.3 kPa is Standart conditions, so 22.4 L is 1 mol, 1 mol anything contains 6.023 x 10^23, 
AnswerA

Answer 2

Ow many oxygen molecules are in 22.4 liters of oxygen gas at 273k and 101.3kpa
First solve the number of moles of the oxygen gas by using the ideal gas equation:
PV = nRT
Where n is the number of moles
n = PV/RT
n = (101 300 Pa) (22.4 L) (1 m3/1000 L ) / ( 8.314 Pa m3 / mol K) ( 273 K)
n = 1 mol O2
the number of molecules can be solve using avogrados number 6.022x10^23 molecule / mole
molecules of one mole O2 = 6.022x 10^23 molecules