What is calcium sulphate?
Answers
Answer:
Calcium sulfate, CaSO4, is a naturally occurring calcium salt. It is commonly known in its dihydrate form, CaSO4∙2H2O, a white or colourless powder called gypsum. As uncalcined gypsum, the sulfate is employed as a soil conditioner.
Explanation:
Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hydrate is better known as plaster of Paris, and another occurs naturally as the mineral gypsum. It has many uses in industry. All forms are white solids that are poorly soluble in water.[6] Calcium sulfate causes permanent hardness in water.
Calcium sulfate
Calcium sulfate anhydrous
Calcium sulfate hemihydrate
Names
Other names
Plaster of Paris
Drierite
Gypsum
Identifiers
CAS Number
7778-18-9 ☑
10034-76-1 (hemihydrate) ☒
10101-41-4 (dihydrate) ☒
3D model (JSmol)
Interactive image
ChEBI
CHEBI:31346 ☑
ChemSpider
22905 ☑
ECHA InfoCard
100.029.000
E number
E516 (acidity regulators, ...)
KEGG
D09201 ☒
PubChem CID
24928
RTECS number
WS6920000
UNII
E934B3V59H ☑
CompTox Dashboard (EPA)
DTXSID9029699 Edit this at Wikidata
InChI
InChI=1S/Ca.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2 ☑
Key: OSGAYBCDTDRGGQ-UHFFFAOYSA-L ☑
InChI=1/Ca.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2
Key: OSGAYBCDTDRGGQ-NUQVWONBAU
SMILES
[Ca+2].[O-]S([O-])(=O)=O
Properties
Chemical formula
CaSO4
Molar mass
136.14 g/mol (anhydrous)
145.15 g/mol (hemihydrate)
172.172 g/mol (dihydrate)
Appearance
white solid
Odor
odorless
Density
2.96 g/cm3 (anhydrous)
2.32 g/cm3 (dihydrate)
Melting point
1,460 °C (2,660 °F; 1,730 K) (anhydrous)
Solubility in water
0.21g/100ml at 20 °C (anhydrous)[1]
0.24 g/100ml at 20 °C (dihydrate)[2]
Solubility product (Ksp)
4.93 × 10−5 mol2L−2 (anhydrous)
3.14 × 10−5 (dihydrate)
[3]
Solubility in glycerol
slightly soluble (dihydrate)
Acidity (pKa)
10.4 (anhydrous)
7.3 (dihydrate)
Magnetic susceptibility (χ)
-49.7·10−6 cm3/mol
Structure
Crystal structure
orthorhombic
Thermochemistry
Std molar
entropy (So298)
107 J·mol−1·K−1 [4]
Std enthalpy of
formation (ΔfH⦵298)
-1433 kJ/mol[4]
Hazards
Safety data sheet
See: data page
ICSC 1589
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
010
Flash point
Non-flammable
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 15 mg/m3 (total) TWA 5 mg/m3 (resp) [for anhydrous form only][5]
REL (Recommended)
TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp) [anhydrous only][5]
IDLH (Immediate danger)
N.D.[5]
Related compounds
Other cations
Magnesium sulfate
Strontium sulfate
Barium sulfate
Related desiccants
Calcium chloride
Magnesium sulfate
Related compounds
Plaster of Paris
Gypsum
Supplementary data page
Structure and
properties
Refractive index (n),
Dielectric constant (εr), etc.
Thermodynamic
data
Phase behaviour
solid–liquid–gas
Spectral data
UV, IR, NMR, MS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).