Why is a mole related to carbon 12? and what is a 'mole of ammonia'? Watch

Kali5
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Hi guys,

I'm relatively new to chem and i'm struggling to understand why mole is related to carbon 12.

I understand that mole is the measurement of quantity, just as we count a 'dozen of eggs'. I have read plenty of websites describing this and it still doesn't make sense to me why carbon 12 is related.

Also, what is meant by the term '1 mole of ammonia'. How can there be 26.022 x 10^23 particles inside an ammonia molecule? Since 1 ammonia molecule has 10 electrons, 10 neurons and 10 protons. So how can there be 602,200,000,000,000,000,000,000 particles in this? Aren't atoms the smallest form compounds can make? They're 3 atoms in ammonia, how can we get such a large number? I'm not getting something here, lol. Any help is really appreciated
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Majime01
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Hi there,

from what I know that carbon 12 has weight which is very close to being exactly 12 unlike other elements which have point something something...... I don’t know I might be wrong here but it’s been a while since I studied chemistry.
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Sinnoh
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A mole is just Avogadro's number of something. A mole of hydrogen means that you have Avogadro's number of hydrogen atoms. A mole of beans would mean you had Avogadro's number of beans. A mole of ammonia means you have Avogadro's number of entire ammonia molecules.

As for why carbon-12 is used, well maybe it's because organic chemistry is a huge part of chemistry.

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charco
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When measuring relative values for any quantity you have to have a reference that is assigned a specific exact value. Historically, various isotopes have been used as the reference for relative mass, hydrogen, oxygen and now it has been internationally agreed (IUPAC) to use the isotope 12C as the reference and to assign its relative mass to be exactly 12.0000.

Now every other particle is compared to this isotope. So if a particle is double the mass of a 12C isotope then it has a relative mass of 2 x 12 = 24

This, in turn, gives us a definition for 1 mol = the number of particles in the relative mass of that substance expressed in grams.
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Lucia12
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TBH I don’t actually know why it was compared to a carbon 12 but I assume it was probably convenience at the time because carbon 12 is stable and somewhat abundant and in an easier state to work with while others were not as easy to obtain or work with because they’re gases or liquids.
As for the other part, protons, neutrons and electrons are sub-atomic particles that make up atoms, not actual atoms. They’re also not the smallest known things coz you’ve also got quarks and neutrinos but those are not important for this.
A mole in chemistry just makes it easier for some calculations than it would be without them. Because an atom is so small it’s weight is also tiny so we time by 6.022x10^23 so it has a mass that is you could weigh out in grams on a normal scale then do experiments and calculations. All a mole is 6.022x10^23 atoms of an element.
A compound is made up of atoms, for example ammonia is made up of 3 hydrogen atoms and 1 nitrogen atom. So the smallest ammonia could be is one compound of NH3. While if you just take an element like copper (Cu) the smallest it could be is one atom of copper big
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Jenniferann232
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No idea why it’s linked to carbon 12, I’d go with what’s been said above.

With the mole of ammonia it means you have 6.022....etc whole molecules of ammonia rather than saying you’ve got 6.022...etc molecules IN the ammonia.

For example a mole of doughnuts would mean I have 6.022x10^23 doughnuts not I’ve got 6.022x10^23 molecules INSIDE my doughnut

I hope that’s helped a bit?
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charco
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(Original post by Jenniferann232)
No idea why it’s linked to carbon 12, I’d go with what’s been said above.

With the mole of ammonia it means you have 6.022....etc whole molecules of ammonia rather than saying you’ve got 6.022...etc molecules IN the ammonia.

For example a mole of doughnuts would mean I have 6.022x10^23 doughnuts not I’ve got 6.022x10^23 molecules INSIDE my doughnut

I hope that’s helped a bit?
The mass of an average doughnut is about 127g (wikipedia) so 1 mol of doughnuts has a mass of 7.65 x 1025 g

Or 7.65 x 1013 MegaTonnes
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Jenniferann232
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(Original post by charco)
The mass of an average doughnut is about 127g (wikipedia) so 1 mol of doughnuts has a mass of 7.65 x 1025 g

Or 7.65 x 1013 MegaTonnes
It was an analogy it didn’t have to be accurate. If I am wrong please correct me as I did my chemistry A level in 2010 (now at uni not doing chem either) but I believed a mole of something was 6.022x10^23 molecules of whatever you were measuring. If that’s incorrect then sorry I thought my memory wouldn’t fail me but I haven’t looked at a chemistry book in 8 years 😂
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charco
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(Original post by Jenniferann232)
It was an analogy it didn’t have to be accurate. If I am wrong please correct me as I did my chemistry A level in 2010 (now at uni not doing chem either) but I believed a mole of something was 6.022x10^23 molecules of whatever you were measuring. If that’s incorrect then sorry I thought my memory wouldn’t fail me but I haven’t looked at a chemistry book in 8 years 😂
No, you were 100% correct.

Just a lot of dough to make them nuts.
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Ryan CS
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Carbon-12 is used because it is relatively abundant and easy to quantify as its solid. A mole is the number of particles of any substance in an amount. e.g. for 12g of Carbon-12 there is one mole or 6.02x10^23 atoms of C-12. Basically one mole is avogadros number (6.02x10^23) so you can have a mole of ammonia which is 6.02x10^23 molecules of ammonia.

Number of Moles =Number of Particles/Avogadro Number
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Your Local Cat
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