How many moles of nickel are in #5.12 * 10^25# atoms of nickel?

1 Answer
Feb 9, 2018

Answer:

#85.0#

Explanation:

The key here is Avogadro's constant, which tells you the number of representative particles present in #1# mole of a substance.

By definition, and this is what Avogadro's constant tells you, #1# mole of nickel must contain #6.022 * 10^(23)# atoms of nickel. In other words, if you don't have #6.022 * 10^(23)# atoms of nickel, you don't have #1# mole of nickel.

Now, your sample contains #5.12 * 10^(25)# atoms of nickel, so you know for a fact that the sample contains more than #1# mole of nickel.

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.