Zero superscript

Because the energy is defined at the atom scale, the standard state is implicit in the definition and the zero superscript is hereafter omitted. 

Another use for the zero integer superscript occurs in the domain of catenanes and rotaxanes. Although the same examples as the ones cited in Schill s monograph [1] for the development of a suitable nomenclature have been selected for discussion, his organizational scheme — which is merely an extension of I.U.P.A.C. s organic chemistry nomenclature — has not been. Instead, the nomenclature developed earlier for more traditional compounds is easily expandable to include these "compounds". Toward this end, note that in the formulation described in Chapter 1, the semi-colon was selected as a co-ordinate separator and the colon as a sub-ordinate separator of strings of nomenclature code. One now needs only to introduce the use of the zero superscript to indicate that the choice of locant numbering is irrelevant. 

The energy released (-2808 kJ) is the enthalpy of combustion. The enthalpy (heat) of combustion (A//j,omb) of a substance is the enthalpy change for the complete burning of one mole of the substance. Standard enthalpies of combustion for several common substances are given in Table 16-5. Standard enthalpy changes have the symbol A//°. The zero superscript tells you that the reactions were carried out under standard conditions. Standard conditions are one atmosphere pressure and 298 K (25 °C) and should not be confused with standard temperature and pressure (STP). 

We now have a standard state for which a zero superscript is applicable ... 

The denominator is stressed, as it shows that a is dimensionless. We have now defined a standard state for which a zero superscript is applicable, and can write a simplified equation, which is widely useful ... 

The singlet and triplet electronic levels are labeled S and T, respectively. Subscripts indicate the order of increasing energy the superscript v indicates that a molecule has an excess vibrational energy absence of a superscript indicates that the vibrational energy of the molecule is in thermal equilibrium a zero superscript indicates that a molecule is in the lowest vibrational level. For clarity, the vibrational and rotational levels are shown equally spaced. 

Note that in normal usage, the zero oxidation state of the solid metal is understood, not shown with a zero superscript. It has been found that with some metals the spontaneous reaction is in the opposite direction and the metal ions tend to become metal atoms, taking up electrons in the process. This reaction can be represented as... 

As follows from the assertions in regularity assumptions 2, 3 (see end of Sect. 4.6 and Rem. 19), the matrix of both derivatives in (4.310) has the (maximal) rankn — h (equilibrium values are stressed here by the zero superscript, i.e. these are the values of corresponding quantities at p", T ). Therefore using now zero reaction rates (4.302) in the result (4.310) we obtain a system of homogeneous linear equations torn —h equilibrium affinities with the matrix of rank n - h formed by the equilibrium values of derivatives dJp/dpy. Therefore chemical affinities of independent chemical reactions (and, consequently, also of dependent reactions) must be zero in equilibrium... 

The use of a superscript zero after an element (e.g., Li°) indicates the element is in an uncharged metallic state (the zero oxidation state). Li°, Na°, and K° are all highly reactive metals we will occasionally encounter in this course—look for the zero superscript (°). 

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