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
cm3·mol-1
ΔGºf
J·mol-1
ΔHºf
J·mol-1
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)
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