Example 3.2: Computing Formula Mass for an Ionic Compound

Solution

The formula for this compound indicates it contains \(\ce{Al^3+}\) and \(\ce{SO4^2-}\) ions combined in a 2:3 ratio. For purposes of computing a formula mass, it is helpful to rewrite the formula in the simpler format, \(\ce{Al2S3O12}\). Following the approach outlined above, the formula mass for this compound is calculated as follows: