# __ amu in 1 g

i_love_science
I don't understand the ratio [ 1 g / 6.02*10^23 amu] in the following conversion factor:

[228.2 amu / 4.75*10^(-23) cm3] * [ 1 g / 6.02*10^23 amu] = 7.98 g/cm3

(This calculation is in a problem where you're finding the density of a unit cell in g/cm3 - though it has nothing to do with the conversion factor itself)

Thanks.

Last edited:

The atomic mass unit ##m_u## is defined as ##1/12## the mass of an atom of ##^{12}C##. Also, a mole is the number ##^{12}C## atoms in ##12\text{g}## of ##^{12}C## ##\implies## the mass of an individual ##^{12}C## atom is ##\mathrm{12g}/N_A## and the atomic mass unit is ##m_u = \mathrm{1g}/N_A##. It follows that$$\frac{1\text{g}}{6.02 \times 10^{23} m_u} = 1$$