g2c said:
So a molecule of hydrogen would have an amount of substance of 2/NA
Yes, but only if you're counting hydrogen atoms. Which is then 2/(6*10^23) moles of H. (using rounded values here)
If you're counting hydrogen molecules, then the single discrete particle is that molecule, and the amount of 1 molecule of H2 is 1/(6*10^23) moles of H2.
g2c said:
and would have a mass of 2/(6*10^23) daltons?
No. It would be 2 daltons. (again, all values rounded)
The concept of moles can be confusing at first. But it helps to realize it's just a number, no different than something like e.g. 'a dozen'.
A dozen is 12 of whatever you're counting.
So e.g. 2 cows are 2/12 of a dozen cows.
2 hydrogen atoms are 2/12 of a dozen hydrogen atoms.
1 H2 molecule is 1/12 of a dozen H2 molecules.
A mole is 6*10^23 of whatever you're counting.
So e.g. 2 cows are 2/6*10^23 of a mole of cows.
2 hydrogen atoms are 2/6*10^23 of a mole of hydrogen atoms.
1 H2 molecule is 1/6*10^23 of a mole of H2 molecules.
A dalton is 1/12 of the mass of a C-12 atom.
Since a C-12 atom has mass of 12 daltons, and a mole (so, 6*10^23) of C-12 atoms has a mass of ``12 grams, it follows that if you have a mole of a different substance, and a single unit of that substance weighs N daltons, then a mole of that substance will weigh N grams.
So e.g. if 1 hydrogen atom has the mass of 1 dalton, a mole of hydrogen atoms weighs 1 gram.
If 1 hydrogen molecule has the mass of 2 daltons, a mole of hydrogen molecules weighs 2 grams.Incidentally, a large cow has a mass of approx. 1 metric ton (10^6 g). A mole of cows would weigh (10^6)*(6*10^23) = 6*10^29 grams. So a single cow's mass in daltons is 6*10^29 daltons.
