Combined and Ideal Gas Laws
The combined gas law or general gas equation is formed by the combination of the three laws, and shows the relationship between the pressure, volume, and temperature for a fixed mass of gas:
With the addition of Avogadro's law, the combined gas law develops into the ideal gas law:
where
- P is pressure
- V is volume
- n is the number of moles
- R is the universal gas constant
- T is temperature (K)
where the constant, now named R, is the gas constant with a value of .08206 (atm∙L)/(mol∙K). An equivalent formulation of this law is:
where
- P is the absolute pressure
- V is the volume
- N is the number of gas molecules
- k is the Boltzmann constant (1.381×10−23 J·K−1 in SI units)
- T is the temperature (K)
These equations are exact only for an ideal gas, which neglects various intermolecular effects (see real gas). However, the ideal gas law is a good approximation for most gases under moderate pressure and temperature.
This law has the following important consequences:
- If temperature and pressure are kept constant, then the volume of the gas is directly proportional to the number of molecules of gas.
- If the temperature and volume remain constant, then the pressure of the gas changes is directly proportional to the number of molecules of gas present.
- If the number of gas molecules and the temperature remain constant, then the pressure is inversely proportional to the volume.
- If the temperature changes and the number of gas molecules are kept constant, then either pressure or volume (or both) will change in direct proportion to the temperature.
Read more about this topic: Gas Laws
Famous quotes containing the words combined, ideal, gas and/or laws:
“Thy knotted and combined locks to part,
And each particular hair to stand on end,
Like quills upon the fretful porpentine.”
—William Shakespeare (1564–1616)
“Cassoulet, that best of bean feasts, is everyday fare for a peasant but ambrosia for a gastronome, though its ideal consumer is a 300-pound blocking back who has been splitting firewood nonstop for the last twelve hours on a subzero day in Manitoba.”
—Julia Child (b. 1912)
“When we can drain the Ocean into mill-ponds, and bottle up the Force of Gravity, to be sold by retail, in gas jars; then may we hope to comprehend the infinitudes of man’s soul under formulas of Profit and Loss; and rule over this too, as over a patent engine, by checks, and valves, and balances.”
—Thomas Carlyle (1795–1881)
“The most mighty of nature’s laws is this, that out of Death she brings Life.”
—Herman Melville (1819–1891)