calculate the number of atoms in each of the following
(i)52 moles of Ar
(ii)52u of He
(iii)52d of He
(1) 52 moles of Ar
We Know
1 mole of Ar = 6.022 X 1023 atoms of Ar
Therefore 52 moles of Ar = 6.022 X 1023 X 52 atoms of Ar
= 3.131 X 1025 atoms of Ar
(2) 52 u of He
The atomic mass of 1 He atom is 4 u. Therefore
4 u of He = 1 atom of He
1 u of He = (1 / 4) atoms of He
52 u of He = (52 / 4) atoms of He
= 13 atoms of He
(3) 52 g of He
The molar mass that is the mass of 6.022 X 1023 atoms of helium is 4g.
Hence 1 mole of He = 4 g of He = 6.022 X 1023 atoms of He
1 g of He = (6.022 X 1023) / 4 atoms of He
52 g of He = (6.022 X 1023X 52 ) / 4 atoms of He
= 7.829 X 1024 atoms of He