2007-09-29 20:47:08 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
Calcium sulfate is a common laboratory and industrial chemical. In the form of γ-anhydrite (a nearly anhydrous form), it is sold as a laboratory desiccant. The hemihydrate (CaSO4.~0.5H2O) is better known as plaster of Paris, while the dihydrate (CaSO4.2H2O) occurs naturally as gypsum. The anhydrous form occurs naturally as β-anhydrite. Depending on the method of calcination of calcium sulfate dihydrate specific hemihydrates are sometimes distinguished: alpha-hemihydrate and beta-hemihydrate[1]. They appear to differ only in crystal size. Alpha-hemihydrate crystals are more prismatic than beta-hemihydrate crystals and when mixed with water form a much stronger and harder superstructure
Plaster of Paris, or simply plaster, is a type of building material based on calcium sulfate hemihydrate, nominally CaSO4·0.5H2O. It is created by heating gypsum to about 150 °C.
2CaSO4·4H2O → 2CaSO4·H2O + 3H2O (released as steam).
A large gypsum deposit at Montmartre in Paris is the source of the name.[1] When the dry plaster powder is mixed with water, it re-forms into gypsum. Plaster is used as a building material similar to mortar or cement. Like those materials plaster starts as a dry powder that is mixed with water to form a paste, which then hardens. Unlike mortar and cement, plaster remains quite soft after drying, and can be easily manipulated with metal tools or even sandpaper. These characteristics make plaster suitable for a finishing, rather than a load-bearing material.
2007-09-29 22:42:13 · answer #1 · answered by Anonymous · 1⤊ 0⤋
Calcium sulfate is a common laboratory and industrial chemical. In the form of γ-anhydrite (a nearly anhydrous form), it is sold as a laboratory desiccant. The hemihydrate (CaSO4.~0.5H2O) is better known as plaster of Paris, while the dihydrate (CaSO4.2H2O) occurs naturally as gypsum. The anhydrous form occurs naturally as β-anhydrite.
2007-09-30 00:56:08 · answer #2 · answered by Anonymous · 0⤊ 0⤋
The amount of water of crystallisation is the difference.
2 moles for normal calcium sulphate, and half a mole for plaster of paris.
2007-09-29 20:50:49 · answer #3 · answered by Gervald F 7 · 0⤊ 0⤋
WHAT? WHY? and you have to ask your self is the answer to this question going to make me a millionaire?
2016-04-06 07:55:28 · answer #4 · answered by Anonymous · 0⤊ 0⤋