Calculate the number of atoms in each of the following: (i) 52 moles of Ar (ii) 52 u of He (iii) 52 g of He

(i) The number of atoms present in 52 mol of Ar are 52 × 6.023 × 10²³ = 3.13 × 10²⁵ atoms
(ii) 52 u of He will contain 52/4 = 13 atoms (as atomic mass of He is 4 amu)
(iii) 52 g of He will contain 52/4 × 6.023 × 10²³ = 7.82 × 10²⁴ atoms.