|Fe with Sulfur|
Iron is a lustrous metal with ferromagnetic properties. Sulfur is a multivalent non-metal. It is found in nature in pure form, as well as in form of sulfide or sulfate minerals. Iron powder reacts with sulfur powder, but if you just mix them resulting mixture can still be separated, either with a magnet using metal properties of iron, or using carbon disulfide as a solvent for sulfur.
Chemical reaction between components yields a new compound with different chemical and physical properties from the mixture ingredients. To initiate the reaction between iron and sulfur, the mixture must be heated by flame or touched with a preheated glass rod. Once the reaction starts it continues spontaneously, generating heat so the reaction mixture starts glowing; no need for further heating. During this reaction iron sulfide is formed, the principal reaction is:
As can be observed from the above reaction, a significant amount of energy is released; reaction is exothermic -iron(II) sulfide is a quite stable compound. However, iron and sulfur can be mixed at room temperature, it requires heat to overcome the activation energy barrier (Ea) - a minimal amount of energy that reactants need to have in order to react with each other.
Heat generated in the reaction is sufficient to cause the remaining sulfur to ignite and to burn with a light blue flame. Sulfur(IV) oxide is the main byproduct of iron(II) sulfide synthesis:
Sulfur(IV) oxide is a toxic gas, so the experiment should be carried out in a fume hood, most conveniently on a ceramic plate because of the heat liberated.