How many moles of nickel are in #5.12 * 10^25# atoms of nickel?
The key here is Avogadro's constant, which tells you the number of representative particles present in
By definition, and this is what Avogadro's constant tells you,
Now, your sample contains
To find the exact number of moles, set up a conversion factor using Avogadro's constant.
#5.12 * 10^(25) color(red)(cancel(color(black)("atoms Ni"))) * "1 mole Ni"/(6.022 * 10^(23)color(red)(cancel(color(black)("atoms Ni")))) = color(darkgreen)(ul(color(black)("85.0 moles Ni")))#
The answer must be rounded to three sig figs, the number of sig figs you have for the number of atoms present in the sample.