What is the primary chemical component of white model plaster used for making study casts when mixed with water?

Explanation

Model plaster, commonly known as white plaster, is mainly composed of calcium sulfate hemihydrate ((CaSO4)2·½H2O). When mixed with water, it sets to form a hard, durable cast used for study models. Other forms such as calcium oxide, calcium carbonate, or calcium sulfate dihydrate are not the primary constituents of model plaster.