Question

How many molecules of o2 are present in 1l of air containing 80%volume of o2 at stp

Answer 1

22.4 litres of air in 100'/, volume contains 1 mole of oxygen molecules.
But for 1 litre of air in 100'/, volume of oxygen contains 1/22.4 moles of O2.
Hence it is asked for 80'/, volume
then O2 molecules are:: 80*22.4/100 moles of O2.
::17.92 moles of O2

Answer 2

22.4 liters of air in 100% volume contains 1 mole of oxygen molecules.
but for 1 liter of air in 100% volume of oxygen contains 1/22.4 moles of O2.
................Hence .......it is asked for 80% volume than O2 molecules are = 80*22.4/100 .. moles of O2 .
17.92 moles of O2