To find the formula mass of tin(ii) chromate we multiply the subscript by the molar mass of that particulat element. If there are no subscript we multiply by 1.
[tex]\begin{gathered} Sn:118.7gmol^{-1}\times1=118.7amu \\ Cr:52.0gmol^{-1}\times1=52.0amu \\ O:16.0gmol^{-1}\times4=64amu \end{gathered}[/tex]Total mass or formula mass of the compound is:
[tex]118.7+52+64=234.7amu[/tex]Dividing each element by the formula mass of the compound gives:
[tex]\begin{gathered} Sn:\frac{118.7amu}{234.7amu}\times100=50.6\% \\ \\ Cr:\frac{52amu}{234.7amu}\times100=22.1\% \\ \\ O:\frac{64amu}{234.7amu}\times100=27.3\% \end{gathered}[/tex]
