Hmontmorillonite(HcNa)

Formula : Na0.6Mg0.6Al1.4Si4O10(OH)2:3.006H2O

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
426.656 191.785 (Ref.: 15bla/vie, 11vie/bla) -6090493 (Ref.: Internal calculation) -6611428 (Ref.: 15bla/vie, 11vie/bla) 480.778 (Ref.: 15bla/vie, 11vie/bla) 544.52 (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.
544.52 0.00 0.00 (Ref.: 15bla/vie, 11vie/bla)
Reaction properties

Hmontmorillonite(HcNa) + 6H+ + 0.994H2O ⇌ 1.4Al+3 + 0.6Mg+2 + 0.6Na+

298.15 K, 1 bar log10K: 4.19 ΔH°r:-118065 J·mol-1 (Ref.: 15bla/vie, 11vie/bla)
T(°C) 0 25 60 100 150 200 250 300
log10K 5.92 4.19 1.91 -0.26 -2.41 -4.16 -5.69 -7.20
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-2331.074150 -0.306336 145970.883743 823.779263 -9012081.939824