Enthalpies of precipitation of silver halides; entropy of the aqueous silver ion
- 1 September 1973
- journal article
- Published by National Institute of Standards and Technology (NIST) in Journal of Research of the National Bureau of Standards Section A: Physics and Chemistry
- Vol. 77A (5) , 569-579
- https://doi.org/10.6028/jres.077a.033
Abstract
The enthalpies of precipitation of silver halides and the enthalpies of solution of AgNO3, KCl, and KBr in H2O were measured in an adiabatic solution calorimeter. From the enthalpy measurements of KCl(c) and KBr(c) in AgNO3(aq), and of AgNO3(c) in KCl(aq), in KBr(aq), and in KI(aq), we calculated (in kJ · mol-1) -65.724, -84.826, and -111.124 for ΔH° pptn(298.15 K) for the averages of the chloride, bromide, and iodide reactions, respectively. A reevaluation of the data for the enthalpy of solution of AgNO3(c) has resulted in our selected best value, Δ H ° ( ∞ ) ( 298.15 K ) = 22.730 + 0.084 kJ ⋅ mol - 1 = 5.433 ± 0.020 kcal ⋅ mol - 1 A table of enthalpies of dilution of AgNO3(aq) is also given. The average standard entropy for the aqueous silver ion at 298.15 K is found to be S ° [ Ag + ( aq ) ] = 73.42 ± 0.20 J ⋅ mol - 1 ⋅ K - 1 = 17.55 ± 0.05 cal ⋅ mol - 1 ⋅ K - 1 . .Keywords
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