copper 1 sulfide formula

This demonstration is great for Year 10 students to relate the concept of the mole to finding the formula for an actual reaction product. They will use quantitative calculations to calculate the exact amount of copper sulfide that is produced when a piece of copper wire reacts with sulfur gas. They will also have the opportunity to see some of the different allotropes (forms) of sulfur.

Cuprous sulfide is an insoluble black mineral with the chemical formula Cu2S. It occurs naturally as the mineral chalcocite and is an important raw material in the production of antifouling paint, solid lubricants and catalytic converters. It is also used in supercapacitor electrodes. It is a monovalent copper ion with an oxidation number of 1+ and is the salt of sulfate anion with a 2- oxidation number.

Safety note: Copper sulfide is toxic by inhalation and irritating to the skin. This experiment should only be carried out in an efficient ducted or re-circulatory fume cupboard. The fumes can also cause headache, dizziness and nausea if inhaled. Wear gloves when handling this substance.

Begin by weighing the copper wire, then cutting an 8 cm length and forming it into a hook that will fit snugly over the lip of a boiling tube. Gently heat the tube and carefully lower the hook into position, clamping it securely. Once the sulfur begins to melt, it will quickly react with the copper to form a dark grey, brittle crystalline compound.