Explanation:
atomic mass of oxygen(O)= 16g
no. of moles=given mass/molar mass
no. of moles=63/32 = 2 mol
but 1 mol of oxygen atom contains 6.022 × 10²³ atoms
therefore, 2mol of O2 = 2×6.022×10²³
= 12.044×10²³ atoms
