How many moles are present in 5 atoms of helium?

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caledon | High School Teacher | (Level 3) Senior Educator

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One of the most difficult concepts for new students of chemistry is the concept of the mole. The mole is really just a representative, named number, like pi, or a dozen. You can have a dozen of anything, or a pi of anything, or a mole of anything. You could have a mole of people or a mole of atoms. The value of a mole is 6.022x 10^23,  which is an extremely large number, but the fact that it's a number makes the term "mole" not very different from the term "dozen".

The problem lies in the fact that this number is so large that it defies common understanding and makes it difficult to comprehend or manipulate. However, since we're just relating numbers to other numbers, and not discussing the values of their meaning, this question becomes a little easier. It's the same as asking how many dozens are in 6: obviously less than a dozen, in this case, half a dozen. 

5 is going to be a significantly smaller fraction of the number 6.022x10^23. We just have to divide and be sure that our answer is much less than 1.

5 atoms / (1 mole/6.022x10^23 atoms) = 8.3x10^-24

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