Question

A mixture contains 20% iron ions by mass. What mass of iron chloride (FeCl) would

Answer 1

Mass of iron chloride (FeCl₂) : 22.68 g

Further explanation

Proust stated the Comparative Law that compounds are formed from elements with the same Mass Comparison so that the compound has a fixed composition of elements

In the same compound, although from different sources and formed by different processes, it will still have the same composition/comparison

With this law, we can calculate how many grams an element is needed to make a compound with a certain mass, as desired

$\tt mass~Fe=\dfrac{Ar~Fe}{MW~FeCl_2}\times mass~FeCl_2$

The iron ions in 50 g mixture :

$\tt 20\%\times 50~g=10~g$

$\tt 10=\dfrac{56}{127}\times mass~FeCl_2\\\\mass~FeCl_2=22.68~g$