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

1 Answer
Stefan V.
Feb 9, 2018

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.

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