What is the composition of the mixture of this reaction?

Answer

Dear Ine,

This is a stoichiometric problem. Assuming that this is a down reaction, we see in the reaction that 1 mole of Fe reacts with 1 mole of S to give one mole of FeS.

With the atomic masses you can calculate how many moles of Fe and S you have for the reaction. The atomic mass of Fe = 55.8 g/mol and for S it is 32.1 g/mol.

14.0 g Fe corresponds to 14/55.8 = 0.251 mol and 2.00 g S corresponds to 0.062 mol

So there is not enough S available to use up all the Fe. The amount of S is (what is called) the limiting factor. The mixture you get will contain 0.062 moles of FeS and 0.189 moles of Fe (being the 0.251 moles from the start minus the 0.062 moles that have reacted off).

In mass that means: 0.189 x 55.8 = 10.5 g Fe and 0.062 x 87.9 (molecular mass of FeS) = 5.45 g FeS

Regards

Patrick Demeyere

Odisee University of Applied Sciences, Ghent technology campus