Click to edit Master subtitle styleChapter 6 – GasesTo describe the state, or condition, of a gas, we must specify four variables: Pressure (P), Volume (V, usually in liters), temperature (T, usually in K), and quantity (moles, n). Pressure is the force per unit area (P = F/A). Atmospheric pressure is measured using a Barometer, in which a pressure of one standard atmosphere (1 atm) will support a column of mercury 760 mm high. This is a pressure of 760 Torr. The SI unit of pressure is the pascale (Pa) (1 atm = 760 mmHg = 760 Torr = 101,325 Pa) Manometers, both open and closed end, are used to measure the pressure of trapped gases. Simple GAS LAWS (below) describe IDEAL GASES, hypothetical gases which obey the gas laws exactly over all ranges of pressure and temperature. In an ideal gas, we assume that the gas particles do not interact and occupy no volume. This is obviously not the case in the real world. Real gases exhibit ideal behavior at low pressures and high temperatures, where particles are far apart and take up negligible amounts of space relative to the whole sample.
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