The Thermochemistry of Inorganic Solids IV. Enthalpies of Formation of Compounds of the Formula MX a Y b
It is found that the standard enthalpies of formation Δf H ○ 298 of double salts of the type MX a Y b are related by a simple additivity relation to Δf H ○ 298 of their binary salts MX c and MY d . For divalent metals M this relation takes the form, Δf H ○ 298(MXY) = 1/2 Δf H ○ 298(MX2)+ 1/2 Δf H...
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Veröffentlicht in: | Journal of physical and chemical reference data 1987-07, Vol.16 (3), p.467-470 |
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Hauptverfasser: | , |
Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | It is found that the standard enthalpies of formation Δf
H
○
298 of double salts of the type MX
a
Y
b
are related by a simple additivity relation to Δf
H
○
298 of their binary salts MX
c
and MY
d
. For divalent metals M this relation takes the form, Δf
H
○
298(MXY) = 1/2 Δf
H
○
298(MX2)+ 1/2 Δf
H
○
298(MY2)+C, with C=−13.4 or −17.6 kJ/mol giving equally good fits to the data. From a lesser number of data for trivalent and tetravalent metals M, one finds again a simple additivity relation of the form Δf
H
○
298(MX
a
Y
b
) =(a
x/z)Δf
H
○
298(MX
z/x
) +(b
y/z)Δf
H
○
298(MY
z/
y
)+C, where x, y, and z are the formal valences of X, Y, and M, respectively, so that z=a
x+b
y, and C=0. For 16 divalent metal compounds average deviations are 5.5 kJ/mol with a maximum deviation of 10.7 kJ/mol. For eight trivalent metal compounds the average deviations are 13.9 kJ/mol with a maximum of 50.6 kJ/mol. For five tetravalent compounds, the average deviations are 3.5 kJ/mol with a maximum of 6.3 kJ/mol. |
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ISSN: | 0047-2689 1529-7845 |
DOI: | 10.1063/1.555801 |