how Avogadro’s constant links relative atomic mass to the actual atomic mass
In: Chemistry
It’s part of how Avogadro’s number is defined.
A single atom of Carbon-12 has 1.9926469e-23 grams.
A mole containing Avogadro’s number of Carbon-12 atoms has a mass of 12.0 grams.
It just makes the amounts more reasonable to deal with mole amounts of things instead of carrying out this huge number of atoms.
Can you give more detail about what you don’t understand about it?
Avogadro’s number is “the number of things in a mole” in the same way that 12 is “the number or things in a dozen”.
*By definition*, 1 mole (Avogadro’s number) of carbon-12 atoms weighs 12 grams. That’s the connection, it’s just the definition. Oh, and for the “actual atomic mass”, we give that in “atomic mass units” which are grams per mole. So again it’s all kind of the same thing.
Alright, imagine you have a big bag of marbles, and each marble represents a tiny particle called an atom. Now, scientists want to figure out how heavy these atoms are compared to each other.
Avogadro’s constant is like a special number that tells us how many marbles (atoms) are in one group. It’s like saying, “In every group, there are exactly this many marbles.” So, if you know the weight of one marble (one atom), you can easily figure out the total weight of all the marbles in the group.
Now, the relative atomic mass is a way of comparing the weight of different types of marbles (atoms). It’s like saying, “This type of marble is a bit heavier than that type.” Avogadro’s constant helps us connect the weight of one marble to the actual weight of all the marbles in a group.
In simpler terms, Avogadro’s constant helps scientists understand and compare the weights of different atoms by giving them a way to count and measure these tiny particles.
It’s a way to try and quantify. Mass itself is made up concept.
Rest mass is dynamic subatomic particles with their kinetic energy restrained into fields like strong /weak nuclear force, gluons, and so on.
For example, when you split the atom, the total mass of the pieces left behind is less than the mass of the atom. The energy binding things together is mass as well.
If you look at cern, they can only accelerate a particle to a particular fraction of the speed of light, after that it just gains mass as you pump energy into it.
A mechanical clock running from energy stored in its spring will weigh more than same non running clock with no energy in the spring.
Technically, molar mass is standardized by the weight of Carbon-12, but that’s not how I learned it when it was first introduced to me in high school. I learned with a simplified explanation.
Each elements mass number is the combination of their protons and neutrons. For simplicity’s sake, we’ll say protons and neutrons have the same mass (they don’t really) and the name of that unit of mass is a Dalton.
Avagadro’s number links Daltons to grams. If you have an Avagadros number of things that individually weigh 1 Dalton, then an Avagadro pile of them (a mole of them) would weigh 1 gram.
So for an element like Lithium for example, it has 3 protons and 3 neutrons, so a single atom weighs ~6 Daltons. If you have an Avagadro’s number of them, then you have a pile of 6 grams of Lithium.
The try usefulness of this relationship shines when you have a sample of some known compound, and just by measuring the weight you will be able to determine the quantity of individual atoms/molecules.
What people are missing here is that atomic mass is consistent.
Hydrogen (generally) just has one proton, helium has 2 protons and 2 neutrons, chlorine has 17 protons and 18 neutrons, etc.
Protons and neutrons basically have the same mass, so we just say they’re the same.
So, if we define a mol of hydrogen to have a mass of 1 gram, then we work backwards and find out how many atoms that is.
And the rest flows from there. An atom with 40 protons and 38 neutrons has a mass 78 times more than the hydrogen atom, so if you have that many atoms of it, it will be 78g.
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