Question

Calculate the numer of molecules for the folloeing:
1) 52g of helium
2) 12.044*10^23 numer of helium atoms

Answer 1

A)13 atoms

and

NO of molecules = 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

B)2 mole

Answer 2

1 atomic weight of helium is 2

no of moles=given weight/molecular weight

= 52/2

=26 moles

1 mole of helium contains 6.022*10^23 atoms

so 26 moles will contain 26*6.022*10^23 atoms

2) no of moles= given no of molecules/Avogadro no

= 12.044*10^23/6.022*10^23

= 2 moles