chemical thermodynamics of neptunium and plutonium - U.S. ...

808 B. Ionic strength correctionsFigure B.1: Plot of log 10 β 1 + 4D vs. I m for Reaction (B.12), UO 2+2+ Cl − ÅUO 2 Cl + at 25 ◦ C and 1 bar. The straight line shows the result of the weighted linearregression, and the dotted lines represent the uncertainty range obtained by propagatingthe resulting uncertainties at I = 0 back to I = 4m.1.41.21Ùlog 10 β1 + 4D0.80.60.40.2Ù Ù ÙÙ Ù ÙÙÙÙÙ Ù ÙÙÙlog 10 β1 ◦ = 0.17 ± 0.02ε =−0.25 ± 0.0200 0.5 1 1.5 2 2.5 3 3.5 4Ionic strength, molalExample B.3:When using the specific ion interaction theory, the relationship between the redox potentialof the couple PuO 2+2 /Pu4+ in a medium of ionic strength I m and the correspondingquantity at I = 0 should be calculated in the following way. The reaction inthe galvanic cellPt | H 2 (g, r) | H + (r) ‖ PuO 2+2 , Pu4+ , H + , H 2 O(l) | PtisPuO 2+2+ H 2 (g, r) + 4H + − 2H + (r) Å Pu 4+ + 2H 2 O(l) (B.14)where the “r” is used to indicate that H 2 (g) and H + are at the chemical conditionsin the reference electrode compartment, i.e., standard conditions when the referenceelectrode is the SHE. However, H + ,H 2 O(l) and the PuO 2+2 /Pu4+ are the conditionsof the experimental measurements (i.e., non-standard conditions, usually high ionicstrength to improve the accuracy of the measurement).For Reaction B.14⎛⎞log 10 K ◦ = log 10⎝ a Pu 4+ × a2 H 2 O × a2 H + (r)⎠a PuO2+2× a 4 H + × f H2 (r)