How does 1 mole of a compound = the molecular weight of the compound?
Well you can actually calculate it like this
$$1\ \mathrm{amu}=1.66\times10^{-27}\ \mathrm{kg}$$
Therefore
$$119\ \mathrm{amu}=119\times1.66\times10^{-27}\ \mathrm{kg}$$
But for 1 mole, multiplying by Avogadro number you get mass of one mole as $$\begin{align}
119\times1.66\times10^{-27}\times6.022\times10^{23}&amp;=0.11899\ \mathrm{kg}\\
&amp;=118.99\ \mathrm g\\
&amp;\approx119\ \mathrm g
\end{align}$$