Problem
Problem
Calcium sulphate is found in nature in two forms, anhydrous calcium sulphate and hydrated calcium sulphate. When anhydrous calcium sulphate is heated with coke, sulphur dioxide gas is obtained. When hydrated calcium sulphate is heated to , it forms anhydrous salt. What is the product formed when hydrated is heated to instead of ? a. b. c. d.Intuitive explanation
When you heat a hydrated salt, water doesn't all leave at once—different amounts of water escape at different temperatures, creating intermediate hydration states. Calcium sulphate hydrate is special: it has a "partial dehydration" point where only some water molecules are removed, leaving a specific lower-hydrate form stable at that intermediate temperature. At , you're heating enough to lose water, but not enough to reach the fully anhydrous form, so you'll get a compound with fewer water molecules than the original but more than zero.
Intuitive explanation
When you heat a hydrated salt, water doesn't all leave at once—different amounts of water escape at different temperatures, creating intermediate hydration states. Calcium sulphate hydrate is special: it has a "partial dehydration" point where only some water molecules are removed, leaving a specific lower-hydrate form stable at that intermediate temperature. At , you're heating enough to lose water, but not enough to reach the fully anhydrous form, so you'll get a compound with fewer water molecules than the original but more than zero.