Mole Definition

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Sydni Stewart
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Mole Definition

Postby Sydni Stewart » Wed Oct 03, 2018 10:51 am

Is there a reason a Mol is defined by 12 grams of carbon-12? What is the significance or is it coincidental?

Andrewwiner4D
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Joined: Fri Sep 28, 2018 12:28 am

Re: Mole Definition

Postby Andrewwiner4D » Wed Oct 03, 2018 10:55 am

This definition was just an example for one element. The atomic weights given on the periodic table are grams per one mole, so if you wanted to look at another element, let's use hydrogen, one mole would equal 1.001 grams of hydrogen.

Hannah Faris 1C
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Joined: Fri Sep 28, 2018 12:18 am

Re: Mole Definition

Postby Hannah Faris 1C » Wed Oct 03, 2018 12:00 pm

From what I heard in a different chemistry course that I've taken, it was chosen on purpose (like as a base? Because carbon-12 is the most common isotope of carbon, the base of life). This is related to the definition of an amu, where 1 amu = 1/12 the mass of a carbon-12 atom. 1 amu=1g/mol which means that 1amu*1mol = 1g, or a mol of amu units is exactly a gram. Therefore 1 mol of carbon 12 atoms = 12.0000 g. So tldr; it's related to the definition of an amu and how that relates to moles and grams.

Sorry for the messy explanation, I hope it helps a little! Basically it isn't just a coincidence it's all part of definitions of stuff.

Nicklas_Wright_1A
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Joined: Fri Sep 28, 2018 12:23 am

Re: Mole Definition

Postby Nicklas_Wright_1A » Wed Oct 03, 2018 7:47 pm

A mole is just like a dozen, but instead of signifying 12 of something, it signifies 6.022x10^23. The reason that this number is used is because 6.022x10^23 amu is equal to 1 gram. This helps make calculations simpler.

Jayde Felix 4H
Posts: 59
Joined: Fri Sep 28, 2018 12:28 am

Re: Mole Definition

Postby Jayde Felix 4H » Wed Oct 03, 2018 8:29 pm

When you have one mole of an atom, it’s a direct translation between its atomic weight and grams.
Ex) 1 mole of Iron-56 = 56 grams

John Kim Lec3Dis3L
Posts: 23
Joined: Fri Sep 28, 2018 12:17 am

Re: Mole Definition

Postby John Kim Lec3Dis3L » Wed Oct 03, 2018 8:57 pm

Nicklas_Wright_3F wrote:A mole is just like a dozen, but instead of signifying 12 of something, it signifies 6.022x10^23. The reason that this number is used is because 6.022x10^23 amu is equal to 1 gram. This helps make calculations simpler.


Well, to add on to what this poster is saying, an AMU is a mass unit equal to 1/12 the mass of a single carbon-12 atom, which is why the mass of 6.022E23 identical carbon-12 atoms is equal to the atomic weight in grams (12g). Also, the C-12 atom is specifically used because carbon-12 is the most common naturally occurring isotope of carbon and is always assumed to be exactly 12.0-repeating AMU.


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