Answer
$392.3$ amu
Work Step by Step
Chromium (III) sulfate has a molecular formula equal to $Cr_2(SO_4)_3$. The molecular mass of the compound is obtained through the atomic masses of the elements (Cr, S, and O) and by the number of atoms of each element.
Therefore,
MM ($Cr_2(SO_4)_3$) =$(2\times52)+(3\times32.1)+(12\times16) =392.3amu$
Note: 392.3 amu or 392.3 u, these are similar nomeclatures.
