Calculate the number of atoms in each of the following:

(a) 52 moles of He

(b) 52 amu of He

(c) 52 g of He

(a) No. of atoms = Moles x 6.022 x 10²³

= 52 × 6.022 x 10²³ = 3.131 × 10²⁵ atoms

(b) 4 amu = 1 atom of He

∴ 52 amu = $\dfrac{52}{4}$ = 13 atoms of He

(c) Mass of 1 mole of He is 4 g

4 g of He contains 6.022 × 10²³ atoms

∴ 52 g of He contains $\dfrac{6.022 \times 10^{23}}{4} \times 52$

= 7.828 × 10²⁴ atoms