Question

How many moles are in 4.64 x 1025 atoms of H2CO3?

Please help! Chemistry is really killing me this unit!

Answer 1

If I asked you, how many dozen eggs there were in a 144 eggses, would you be able to tell me? The `"mole"` is PRECISELY the same sort of collective number as the `"dozen"`.

Explanation:

The given question is not sound, in that you SHOULD have asked how many moles there were in `4.64xx10^25` `"molecules of carbonic acid"` (i.e. `"molecules NOT atoms"`).

Now we know that a mole of stuff contains `6.022xx10^23` individual items of that stuff (how do we know, well, your chemistry teacher will try to beat it into your brains, and the number WILL ALWAYS appear as supplementary material in a chemistry exam). And so we take the quotient...

`(4.64xx10^25*"molecules of carbonic acid")/(6.022xx10^23*"molecules of carbonic acid"*mol^-1)=`

`=77.05*mol*"carbonic acid"`.

And given that we know that `"carbonic acid"` has a molar mass of `62.03*g*mol^-1` (and note that you cannot isolate this as a solid)...we gots a mass of...

`77.05*molxx62.03*g*mol^-1-=4779.5*g`

And back to the number, so-called `N_A`: `6.022xx10^23` individual hydrogen atoms, `"^1H`, have a MASS of `1*g`. And thus `"Avogadro's number"` is the link between between the micro world of atoms and molecules to the macro world of grams and litres.