Bar (unit) (symbol: cbar), and millibar (symbol: mbar or mb). The notation bar(g), though deprecated by various bodies, represents gauge pressure, i.e., pressure in bars above ambient or atmospheric pressure. The bar is defined using the SI derived unit, pascal: ≡ 100,000 Pa ≡ 100,000 N/m. Thus, is equal to: and 1 bar is approximately equal to: Notes: The word "bar" has its origin in the Greek word (), meaning weight. The unit's official symbol is bar; the earlier symbol b is now deprecated and conflicts with the use of b denoting the unit barn, but it is still encountered, especially as
Standard enthalpy of formation Standard enthalpy of formation The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements, with all substances in their standard states. The standard pressure value "p" = 10 Pa (= 100 kPa = 1 bar) is recommended by IUPAC, although prior to 1982 the value 1.00 atm (101.325 kPa) was used. There is no standard temperature. Its symbol is Δ"H". The superscript Plimsoll on this symbol indicates that the process has occurred under standard conditions at the specified temperature