Fundamentals E.17

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Fundamentals E.17

Postby 104785906 » Fri Jun 30, 2017 1:32 am

The question asks for which sample in the pair contains the greater number of moles:

7.36x10^27 atoms of Ru or 7.36x10^27 atoms of Fe ? I attempted this problem following the basic order of conversion but its off having that since one would multiply by 1 mole and then divide by 6.022X10^23, it gives the same answer. Or perhaps I'm not converting correctly, may someone please explain.

Matthew Leung 1B
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Re: Fundamentals E.17

Postby Matthew Leung 1B » Fri Jun 30, 2017 9:10 am

1 mole of objects means 6.0221 * 10^23 of those objects, in this case, 7.36 * 10^27 atoms of Ru and 7.36 * 10^27 atoms of Fe contain the same number of moles: 7.36 * 10^27 / 6.0221 * 10^23 = 0.0122 * 10^6 hope this helps:)

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Re: Fundamentals E.17

Postby Daniela_Chem14A » Fri Jun 30, 2017 3:21 pm

In expressing our final answer, are we allowed to leave it as 0.0122 * 10^6 or do we have to write it as 1.22x10^4?

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Re: Fundamentals E.17

Postby Chem_Mod » Fri Jun 30, 2017 4:54 pm

The latter would likely be preferred, but since they're the same answer it shouldn't matter. When in doubt, simplify the expression as much as possible.

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Re: Fundamentals E.17

Postby Andre_Galenchik_2L » Thu Oct 04, 2018 12:12 am

When asked questions about comparing atoms, grams, or moles in this case, just always take the time to use Avogadro's number and the molar mass to get the unit that you want. Using dimensional analysis can help you cross out units and see if the unit that is remaining is the one you want (such as the unit being moles when you need to use or find the number of moles of a molecule).

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