Gypsum

Formula : CaSO4:2H2O

Family: 
Sulfates
Space group: 
Monoclinic - Prismatic H-M Symbol (2/m) Space Group: A2/a
Dana class: 
29.6.3.1 (29) Hydrated Acid and Sulfates (29.6)where A XO4 . x(H2O) (29.6.3) Dana Group
High temperature: 
Stable at room temperature
Geological context: 
Gypsum is one of the more common minerals in sedimentary environments. It is a major rock forming mineral that produces massive beds, usually from precipitation out of highly saline waters. Since it forms easily from saline water, gypsum can have many inclusions of other minerals and even trapped bubbles of gas and water. Occus as a ageing products in mineral waste, slags, MSWI bottom ash, or as secondary product from APC processes.

Dernière mise à jour le 25.01.2021

THERMODYNAMICS

Individual properties (298.15 K)
M
g·mol-1
 V°
cm3·mol-1
 ΔGºf
J·mol-1
 ΔHºf
J·mol-1
 Sº
J·mol-1·k-1
 CP
J·mol-1·K-1
172.172 74.690 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp. -1797387 (Ref.: Internal calculation) -2022946 (Ref.: CODATA87) Garvin D., Parker V.B and White H.J., 1987. CODATA Series on Thermodynamic Properties, Hemisphere, Washington, DC. 193.930 (Ref.: CODATA87) Garvin D., Parker V.B and White H.J., 1987. CODATA Series on Thermodynamic Properties, Hemisphere, Washington, DC. 186.20 (Ref.: 74nau/ryz) Naumov G.B., Ryzhenko B.N., and Khodakovsky I.L., 1974. Handbook of Thermodynamic Data. U.S. Geol. Surv.WRD 74 001, 328 pp.
CP(T) = a + b·T + ·c·T-2 (T in Kelvin)
a
J·mol-1·K-1
 b * 103
J·mol-1·K-2
 c * 10-5
J·K·mol-1
 Maier Kelley Ref.
186.20 0.00 0.00 (Ref.: 74nau/ryz) Naumov G.B., Ryzhenko B.N., and Khodakovsky I.L., 1974. Handbook of Thermodynamic Data. U.S. Geol. Surv.WRD 74 001, 328 pp.
Reaction properties

Gypsum ⇌ Ca+2 + SO4-2 + 2H2O

298.15 K, 1 bar log10K: -4.60 ΔH°r:-1054 J·mol-1 (Ref.: CODATA87) Garvin D., Parker V.B and White H.J., 1987. CODATA Series on Thermodynamic Properties, Hemisphere, Washington, DC.
T(°C) 0 25 60 100 150 200 250 300
log10K -4.66 -4.60 -4.71 -4.99 -5.48 -6.14 -7.00 -8.22
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-1620.206983 -0.257234 89150.211143 587.382464 -5347327.619493