Quasi-ice-like C(p) behavior of molecular H(2)O in hemimorphite Zn(4)Si(2)O(7)(OH)(2)center dot H(2)O: C(P) and entropy of confined H(2)O in microporous silicates

Geiger, C. A. and Dachs, E. (2009) Quasi-ice-like C(p) behavior of molecular H(2)O in hemimorphite Zn(4)Si(2)O(7)(OH)(2)center dot H(2)O: C(P) and entropy of confined H(2)O in microporous silicates American Mineralogist, 94 (4). pp. 634-637. DOI 10.2138/am.2009.3138.

Full text not available from this repository.

Supplementary data:

Abstract

Hemimorphite, Zn(4)Si(2)O(7)(OH)(2)center dot H(2)O, and its dehydrated analog Zn(4)Si(2)O(7)(OH)(2) were studied by low-temperature relaxation microcalorimetry and their heat capacity determined to analyze the behavior of the confined H(2)O between 5 and 300 K. An analysis of the data, which are corrected for the presence of a phase transition, shows that the C(p) of H(2)O in hemimorphite behaves more similar to the C(p) of ice than to liquid water or steam. The H(2)O molecule, with its four planar hydrogen bonds in hemimorphite, as well as its tetrahedral coordination in ice, is more rigidly hydrogen bonded in both than in liquid water. This is reflected in their respective Cp behavior. The heat capacity and entropy for the dehydration reaction at 298 K are Delta C(p)(rxn)= -2.1 +/- 3.6 P(mol.K) and Delta S(TXn) = 134.7 +/- 4.0 J(mol.K). C(p) behavior at 0 < T < 300 K and entropy values at 298 K for confined H(2)O in hernimorphite and hydrous Mg cordierite are compared to those in several zeolites. The entropy for confined H(2)O in hemimorphite, analcime, and mordenite is around 54 J/(mol.K)at 298 K. The strength of the interactions (e.g., H bonding) between an H(2)O molecule and its surroundings increases approximately from steam > cordierite > analcime > hemimorphite mordenite > heulandite > natrolite approximate to scolecite > liquid H(2)O > ice and, in the case of microporous silicates, is inversely proportional to the S of the confined H(2)O.

Document Type: Article
Keywords: Hemimorphite heat capacity entropy microporous minerals confined H(2)O pulse calorimetric technique thermodynamic properties heat-capacity phase-transition ir spectroscopy 3rd law zeolites natrolite minerals water
Research affiliation: Kiel University
Refereed: No
DOI etc.: 10.2138/am.2009.3138
ISSN: 0003-004X
Date Deposited: 22 Dec 2011 05:36
Last Modified: 08 Oct 2012 10:09
URI: http://eprints.uni-kiel.de/id/eprint/15778

Actions (login required)

View Item View Item