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.

Explanation

(i) 1 mol of Ar contains `=6.022 xx 10^(23)` molecules
52 mol of Ar will contain `=6.022 xx 10^(23) xx 52` atoms
`=3.13 xx 10^(25)` atoms
(ii) 4u of He = 1 atom
52 u of He `=1/4 xx 52 =13` atoms
(iii) 4 g of He contain `=6.022 xx 10^(23)` atoms
52 g of He will contain `=(6.022 xx 10^(23) xx 52)/4` atoms
`=7.83 xx 10^(24)` atoms