How many moles of helium are 8.84*10^24 atoms of He?

14.77 mol.

Explanation:

It is known that every 1.0 mole of compound or element contains Avogadro's number (6.022 x 10²³) of molecules or atoms.

Using cross multiplication:

1.0 mole of He contains → 6.022 x 10²³ atoms.

? mole of He contains → 8.84 x 10²⁴ atoms.

∴ The no. of moles of He contains (8.84 x 10²⁴ atoms) = (1.0 mol) (8.84 x 10²⁴ atoms) / (6.022 x 10²³ atoms) = 14.77 mol.