Q20P - Chemistry: Molecular Nature Of Matter And Change

Question

Fluorite, a mineral of calcium, is a compound of the metal with fluorine. Analysis shows that a 2.76-g sample of fluorite contains 1.42 g of calcium. Calculate the (a) mass of fluorine in the sample; (b) mass fractions of calcium and fluorine in fluorite; (c) mass percents of calcium and fluorine in fluorite.

Step-by-Step Solution

Answer

a) Mass of fluorine in the fluorite sample = 1.34 g

b) Mass fraction of calcium = 0.515 and of fluorine = 0.485

c) Mass percent of calcium = 51.5% and mass percent of fluorine = 48.5%

Step 1: Mass of fluorine in Fluorite

Fluorite is a mineral of Ca and fluorine with the formula CaF₂. As it contains only calcium and fluorine. Hence, the mass of fluorine can be calculated as:

 $$\begin{gathered} \mathbf{Mass}\mathbf{ }\mathbf{of}\mathbf{ }\mathbf{fluorine}\mathbf{ }\mathbf{=}\mathbf{ }\mathbf{Mass}\mathbf{ }\mathbf{of}\mathbf{ }\mathbf{fluorite}\mathbf{-}\mathbf{Mass}\mathbf{ }\mathbf{of}\mathbf{ }\mathbf{calcium} \\ \mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{=}\mathbf{2}\mathbf{.}\mathbf{76}\mathbf{ }\mathbf{g}\mathbf{-}\mathbf{1}\mathbf{.}\mathbf{42}\mathbf{ }\mathbf{g}\mathbf{=}\mathbf{1}\mathbf{.}\mathbf{34}\mathbf{ }\mathbf{g} \end{gathered}$$

Step 2: Mass Fractions

 The formula for mass fraction: 

 $\mathbf{Mass}\mathbf{ }\mathbf{fraction}\mathbf{=}\frac{\mathbf{Mass}\mathbf{ }\mathbf{of}\mathbf{ }\mathbf{componenet}}{\mathbf{Total}\mathbf{ }\mathbf{Mass}}$

 Mass fraction of calcium and fluorine can be calculated as,

 $$\begin{gathered} \mathbf{Mass}\mathbf{ }\mathbf{fraction}\mathbf{ }\mathbf{of}\mathbf{ }\mathbf{calcium}\mathbf{=}\frac{\mathbf{1}\mathbf{.}\mathbf{42}}{\mathbf{2}\mathbf{.}\mathbf{76}}\mathbf{=}\mathbf{0}\mathbf{.}\mathbf{515} \\ \mathbf{Mass}\mathbf{ }\mathbf{fraction}\mathbf{ }\mathbf{of}\mathbf{ }\mathbf{fluorine}\mathbf{=}\frac{\mathbf{1}\mathbf{.}\mathbf{34}}{\mathbf{2}\mathbf{.}\mathbf{76}}\mathbf{=}\mathbf{0}\mathbf{.}\mathbf{485} \end{gathered}$$

Step 3: Mass Percent Calculation

The formula for mass percent is given as

 $\mathbf{Mass}\mathbf{ }\mathbf{percent}\mathbf{=}\frac{\mathbf{Mass}\mathbf{ }\mathbf{of}\mathbf{ }\mathbf{component}}{\mathbf{Total}\mathbf{ }\mathbf{Mas}\mathbf{ }\mathbf{s}}\mathbf{\times }\mathbf{100}$

 The mass percent of calcium and fluorine can be calculated as,

$$\begin{gathered} \mathbf{Mass}\mathbf{ }\mathbf{percent}\mathbf{ }\mathbf{of}\mathbf{ }\mathbf{calcium}\mathbf{=}\frac{\mathbf{1}\mathbf{.}\mathbf{42}}{\mathbf{2}\mathbf{.}\mathbf{76}}\mathbf{\times }\mathbf{100}\mathbf{=}\mathbf{51}\mathbf{.}\mathbf{5}\mathbf{\%} \\ \mathbf{Mass}\mathbf{ }\mathbf{percent}\mathbf{ }\mathbf{of}\mathbf{ }\mathbf{fluorine}\mathbf{=}\frac{\mathbf{1}\mathbf{.}\mathbf{34}}{\mathbf{2}\mathbf{.}\mathbf{76}}\mathbf{\times }\mathbf{100}\mathbf{=}\mathbf{48}\mathbf{.}\mathbf{5}\mathbf{\%} \end{gathered}$$