Why does sulphur lose weight when wet and gains weight on burning?

Answer 1

Sulfur loses weight when wet because it can form soluble compounds, such as sulfates, which dissolve in water and are lost from the solid mass. During burning, sulfur reacts with oxygen to form sulfur dioxide (SO₂), which is a gaseous product. If the burning occurs in an open system, it may seem like it gains weight due to the reaction with oxygen, but in reality, it is the conversion of solid sulfur to a gaseous product that can lead to a net loss in mass if not contained. Thus, the apparent weight changes are due to the transitions between solid, liquid, and gaseous states, as well as the loss of byproducts.