Hmontmorillonite(HcMg)

Formula : Mg0.3Mg0.6Al1.4Si4O10(OH)2:5.129H2O

Space group: 
Monoclinic - Prismatic HM symbol (2/m) Space Group: C 2/m
Dana class: 
71.3.1b.2VIII- 71 Phyllosilicate Minerals ; 71.3 Phyllosilicates Phyllosilicate Sheets of Six-Membered Rings with 2:1 clays ; 71.3.1b Smectite group (Trioctahedral Smectites)
High temperature: 
Low temperature mineral. At higher temperatures(> 500C), detachment of (OH) ions takes place.
Geological context: 
Montmorillonite and beidellite are the principal constituents of bentonite clay deposits. Montmorillonite results from the weathering of basic rocks mainly in conditionsof poordrainage when magnesium is not removed.

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
458.400 225.948 (Ref.: 15bla/vie, 11vie/bla) -6581542 (Ref.: Internal calculation) -7216428 (Ref.: 15bla/vie, 11vie/bla) 572.807 (Ref.: 15bla/vie, 11vie/bla) 693.63 (Ref.: 15bla/vie, 11vie/bla)
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.
693.63 0.00 0.00 (Ref.: 15bla/vie, 11vie/bla)
Reaction properties

Hmontmorillonite(HcMg) + 6H+ ⇌ 1.4Al+3 + 0.9Mg+2 + 4H4SiO4 + 1.129H2O

298.15 K, 1 bar log10K: 2.76 ΔH°r:-115778 J·mol-1 (Ref.: 15bla/vie, 11vie/bla)
T(°C) 0 25 60 100 150 200 250 300
log10K 4.45 2.76 0.52 -1.63 -3.78 -5.54 -7.11 -8.65
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-2328.443604 -0.307706 145518.701915 822.855181 -8998392.131948