## Chemistry: Molecular Approach (4th Edition)

Use the percent composition of mass as a conversion factor to find the mass of fluorine. $100\%$ copper(II) fluoride = $37.42\%$ fluorine. $55.5 g$ copper (II) fluoride $\times \frac{37.42\%-fluorine}{100\%-copper(II)-fluoride} = 20.8$ g $fluorine$.