Derive the formula for a gaseous compound, the mass fraction of tungsten in which is 61.745%

| September 6, 2021 | education

Derive the formula for a gaseous compound, the mass fraction of tungsten in which is 61.745%, and fluorine – 38.255%. Its relative density for hydrogen is 149.

Mass ratio of elements in an unknown compound:

w (W): w (F) = 61.745: 38.255

Taking into account the atomic masses of the elements, let’s move from the mass ratio to the quantitative one:

n (W): n (F) = w (W) / M (W): w (F) / M (F) = 61.745 / 184: 38.255 / 19 = 0.335: 2.013 = 1: 6

This means that in an unknown compound there are 6 fluorine atoms per 1 tungsten atom and its formula can be written as WnF6n.

Molecular weight of unknown compound:

M (WnF6n) = M (H2) * DH2 (WnF6n) = 2 * 149 = 298 (amu).

Let’s compose and solve the equation:

184 * n + 19 * 6n = 298

298n = 298, whence n = 1

and the compound formula: WF6 (tungsten (VI) fluoride).



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