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

14 2. Standards, Conventions, and Contents of the Tables• The designator (sln) is used for substances in solution without specifying theactual equilibrium composition of the substance in the solution. Note the differencein the designation of H 2 OinEqs.(2.2) and(2.3). H 2 O(l) in Reaction (2.2)indicates that H 2 O is present as a pure liquid, i.e., no solutes are present, whereasReaction (2.3) involves a HCl solution, in which the thermodynamic propertiesof H 2 O(sln) may not be the same as those of the pure liquid H 2 O(l). In dilutesolutions, however, this difference in the thermodynamic properties of H 2 O canbe neglected, and H 2 O(sln) may be regarded as pure H 2 O(l).Example:UOCl 2 (cr) + 2HBr(sln) Å UOBr 2 (cr) + 2HCl(sln) (2.1)UO 2 Cl 2 · 3H 2 O(cr) Å UO 2 Cl 2 · H 2 O(cr) + 2H 2 O(l) (2.2)UO 3 (γ ) + 2HCl(sln) Å UO 2 Cl 2 (cr) + H 2 O(sln) (2.3)• The designators (cr), (am), (vit), and (s) are used for solid substances. (cr) isused when it is known that the compound is crystalline, (am) when it is knownthat it is amorphous, and (vit) for glassy substances. Otherwise, (s) is used.• In some cases, more than one crystalline form of the same chemical compositionmay exist. In such a case, the different forms are distinguished by separate designatorsthat describe the forms more precisely. If the crystal has a mineral name,the designator (cr) is replaced by the first four characters of the mineral name inparentheses, e.g., SiO 2 (quar) for quartz and SiO 2 (chal) for chalcedony. If thereis no mineral name, the designator (cr) is replaced by a Greek letter precedingthe formula and indicating the structural phase, e.g., α-UF 5 , β-UF 5 .Phase designators are also used in conjunction with thermodynamic symbols todefine the state of aggregation of a compound a thermodynamic quantity refers to.The notation is in this case the same as outlined above. In an extended notation (cf.[82LAF]) the reference temperature is usually given in addition to the state of aggregationof the composition of a mixture.Example: f G ◦ m (Na+ , aq, 298.15 K)Sm ◦ (UO 2SO 4 · 2.5H 2 O, cr, 298.15 K)Cp,m ◦ (UO 3,α,298.15 K) f H m (HF, sln, HF · 7.8H 2 O)standard molar Gibbs energy of formation ofaqueous Na + at 298.15 Kstandard molar entropy of UO 2 SO 4 · 2.5H 2 O(cr)at 298.15 Kstandard molar heat capacity of α-UO 3 at298.15 Kenthalpy of formation of HF diluted 1:7.8 withwater