Calculate the number of atoms in each of the following (1) 52 moles of Ar
(2) 52u of He.

Explanation

(1) 1 mol Ar`=6.022xx10^(23)` no. of Ar-atoms
`therefore` 52 mol Ar`=52xx6.022xx10^(23)` Ar-atoms
`=3.131xx10^(25)` no Ar-atoms
(2) Mass of 1 He-atom =4u
Therefore, 4u=mass of 1 He-atom
`therefore` 52u He=mass of `(52)/(4)` He-atoms=mass of 13 He-atoms.