Mass of one atom of an element = 6.645 × 10-23 g = Atomic mass.
Mass of given element = 0.320 kg
Number of moles = Mass/ Atomic mass
= (0.320 x 1000)g / (6.645 x 10-23)g
= (320 x 1023) / 6.645
= 48.156 x 1023
= 4.8156 x 1024 moles.
= 48.156 x 10-23
= 4.8156 x 10-24 moles.