Superscript degree symbol

Now we have two functions that can be used to predict spontaneity the entropy of the universe, which applies to all processes and free energy, which can be used for processes carried out at constant temperature and pressure. Since so many chemical reactions occur under the latter conditions, the free The superscript degree symbol (°) in- energy function is more useful to chemists. 

Enthalpy (H) is defined as the heat content of a substance at constant pressure. We cannot know absolute values of H, only differences in the enthalpies of substances. The enthalpy of formation, AHf of a substance at 25°C (298.15 K) and 1 bar pressure is its heat of formation from the elements in their most stable forms at that temperature and pressure. Here, and generally, the superscript degree symbol to the right of the state function denotes that the function is for 1 bar pressure. AHf for the elements in their most stable forms is taken as zero by definition at any temperature and 1 bar pressure. For example, AH° = 0 for rhombic sulfur, the most stable form of sulfur at 1 bar and 25°C. Monoclinic sulfur, with AHf = 0.071 kcal/mol at 1 bar and 25°C is unstable relative to the rhombic form. 

The superscript degree symbol (°) indicates all substances are in their standard states. 

A superscript degree symbol (o) denotes a standard quantity or standard-state conditions. An alternative symbol for this purpose, used extensively outside the U.S., is a superscript Plimsoll mark ( ). ... 

Abbreviations mp, melting point bp, boiling point lit., literature value and dec, decomposition. A full space is used between the number and the unit °C the degree symbol is closed up to the C. A superscript number after lit. denotes the number of the reference. 

Spacing, hyphens, and italics. When a unit symbol is given after a number, a space is always left between the number and the symbol with the exception of cases where the symbol appears in the superscript position, such as degree, minute, and second of plane angles. The symbol for degree Celsius may be written either with or without a space before the degree symbol. For example,... 

Recall that for purposes of tabulating thermodynamic data, certain standard states are chosen, which are indicated by a superscript degree sign on the symbol of the quantity. The standard states are as follows for pure liquids and solids, 1 atm pressure for gases, 1 atm partial pressure for solutions, 1 M concentration. The temperature is the temperature of interest, usually 25°C (298 K). 

In an attempt to be consistent with accepted chemistry nomenclature, Roman numeral superscripts to the right of element symbols (e.g. Biv) will frequently be used to indicate oxidation number and to emphasize that this number does not suggest any particular degree of ionization. This paper contains some discussion of the meaning of these superscripts. 

The usual degree superscript used to designate a standard Gibbs energy is omitted on the symbol AG to avoid a cumbersome symbol. 

The symbol for the Celsius and Fahrenheit degrees is and it is placed as a superscript after the number and before the symbol for the scale. Thus, 10.0°C means 10.0 degrees Celsius. The degree sign is not used with Kelvin temperatures ... 

It is expected that numbers, symbols, and unit abbreviations will be used in the written report. Learn to use the symbols and the equation editor in your word processor, and learn to insert symbols, superscripts, and subscripts in plotting software. For example, use 5°C, not five degrees C. Write 25 million/yr instead of 25 million dollars per year. Include lead zeroes in all numbers less than 1, e.g., 0.25 instead of. 25. Use 10 m instead of 10 in both the report and on figures. Items like m/ 3 are considered unacceptable for reports in this Department. 

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