Answer
A. platinum (IV) oxide, 227.09 amu
B. dinitrogen pentoxide, 108.02 amu
C. aluminum chlorate, 277.33 amu
D. phosphorus pentabromide, 430.47 amu
Work Step by Step
Find the formula mass by adding up the atomic weights of every atom that appears in the molecule.
Example for A: 2 (15.999) + 195.094 = 227.08
Adding Roman numerals in parenthesis is only necessary when the cation can have different charges. Add Greek prefixes to both atoms in molecular compounds to account for their number. For ionic compounds, write the cation followed by the anion ending with "-ide"