Question #72e9a

1 Answer
Stefan V.
May 27, 2016

5.1⋅10−3moles

Explanation:

All you have to do here is use Avogadro's number as a conversion factor to help you find the number of moles that would contain that many atoms of iron.

As you know, Avogadro's number tells you how many atoms you get per mole of a given substance. More specifically, you should know that

∣∣ ∣∣¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯aa1 mole=6.022⋅1023atomsaa∣∣−−−−−−−−−−−−−−−−−−−−−−−−−−−−→ Avogadro's number

Simply put, in order to have one mole of an element, you need to have 6.022⋅1023 atoms of that element. This will be your conversion factor.

So, 3.1⋅1021 atoms of iron would be equivalent to

3.1⋅1021atoms Fe⋅Avogadro's number1 mole Fe6.022⋅1023atoms Fe=∣∣ ∣∣¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯aa5.1⋅10−3moles Feaa∣∣−−−−−−−−−−−−−−−−−−−−

The answer is rounded to two sig figs.

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