Question

How many atoms of ca-46 would be found in a 25.0 g sample of naturally occurring calcium ?

Answer 1

The  number of  ca-46  atoms   found  in   25.0 g   sample  is calculated     as follows

find  the  moles  of   Ca=  25/46  =0.543  moles

by   use of  Avogadro  law    
1 mole =  6.02  x10^23  atoms  what  about   0.543   moles

= 0.543moles/1mole  x (6.02x10^23)atoms  =  3.27  x10  ^23  atoms