Pascal (unit) Pascal (unit) The pascal (symbol: Pa) is the SI derived unit of pressure used to quantify internal pressure, stress, Young's modulus and ultimate tensile strength. It is defined as one newton per square metre. It is named after the French polymath Blaise Pascal. Common multiple units of the pascal are the hectopascal (1 hPa = 100 Pa) which is equal to one millibar, and the kilopascal (1 kPa = 1000 Pa) which is equal to one centibar. The unit of measurement called standard atmosphere (atm) is defined as . Meteorological reports typically state atmospheric pressure in millibars. The unit is
Henry's law a species in the aqueous phase, and formula_8 is the partial pressure of that species in the gas phase under equilibrium conditions. The SI unit for formula_12 is mol/(m Pa); however, often the unit M/atm is used, since formula_17 is usually expressed in M (1 M = 1 mol/dm) and formula_8 in atm (1 atm = 101325 Pa). The Henry solubility can also be expressed as the dimensionless ratio between the aqueous-phase concentration formula_17 of a species and its gas-phase concentration formula_24: For an ideal gas, the conversion is: where formula_27 is the gas constant and formula_28 is the temperature.