Question

Why does 1 amu = 1 g/mol?

Answer 1

Due to the definitions...

Explanation:

The mole is defined as the number of particles in `12 \ "g"` of carbon-`12`, known as `""^12C`. So, we say that in one mole of carbon-`12`, the sample has a mass of `12 \ "g"`.

In other words,

`"mass of carbon-12"=12 \ "g/mol"`.

Still with me? Good.

Now, we also know that the mass of a single carbon-`12` atom is exactly `12 \ "amu"`, as it is an isotope.

And so,

`"mass of carbon-12"=12 \ "amu/atom"`

Combining, we have:

`12 \ "amu/atom"=12 \ "g/mol"`

`=>1 \ "amu/atom"=1 \ "g/mol"`

Therefore we just proved that an atomic mass unit is the same thing as grams per mole. Hope this helps!

For a further explanation, visit:

https://chemistry.stackexchange.com/questions/13764/amu-and-g-mol-relation