Question

how many oxygen atoms are in 4 moles of O2 molecules

Answer 1

Number of atoms/molecules is found by multiplying the number of mole with Avogadro's number.

Answer 2

Note that for this one, using that formula will get you the number of molecules, since you measured oxygen gas(oxygen atoms existing as diatomic molecules).

Answer 3

1 mole of O2 contains = 2* 6.023 *10^23 atoms of O
4 mole of O2 = can u find it now ?