Question

A sample of a compound contains 259.2 g `F` and 40.8 g `C`. How do you find its empirical formula?

Answer 1

`"CF"_4`

Explanation:

We're asked to find the empirical formula of a compound, given the mass of each element present in the compound.

To to this, we need to find the ratio of mole values for each element, so using the molar mass of each element (from a periodic table), let's find the number of moles of each element present:

• `259.2cancel("g F")((1color(white)(l)"mol F")/(19.00cancel("g F"))) = color(red)(13.64` `color(red)("mol F"`

• `40.8cancel("g C")((1color(white)(l)"mol C")/(12.01cancel("g C"))) = color(blue)(3.397` `color(blue)("mol C"`

The ratio of `"F"` atoms to `"C"` atoms is thus

`(color(red)(13.64))/(color(blue)(3.397)) = 4.02 ~~ color(green)(4`

Thus, there are `4` `"F"` atoms for each `"C"` atom, so the empirical formula is

`"CF"_ (color(green)(4))`