Question

How many molecules and atoms of oxygen are present in 5.6 liters of oxygen (O2) at STP?

Answer 1

2.5 you're welcome !!$!

Answer 2

Each mole is 22.4 liters in STP.
So 5.6L is 0.25 moles of O2.
Each mole has 6.022*10^23 molecules(avogadros number)
So 1.505*10^23 molecules of O2 and 3.01*10^23 atoms of oxygen(O).

Hope this helps