The molecular formula of the compound is , from the molecular formula it is clear that 1 mol of contains 3 mol of oxygen.
Also, in 1 mol there are atoms thus, 3 mol of oxygen will have atoms of oxygen.
Thus, there are atoms of oxygen present in 1 mol of .
1 atom of oxygen will be there in mol.
Number of oxygen atoms given is thus, this will be present in of .
Molar mass of is 125.388 g/mol, thus, mass can be calculated as follows:
Rearranging the above equation,
Putting the values,
Therefore, the mass of is 2.16 g.