A real gas behaves like an ideal gas at low pressure and very high temperature. Air is a perfect gas. A perfect gas is also an ideal gas that follows the equation of states of the ideal gas, i.e. PV = mRT all temperatures. With a solid gas mass at constant temperature, the volume is inversely proportional to the pressure. It indicates that at constant volume, the pressure of a fixed amount of a gas varies directly with temperature. The law of combined gases or the general equation of gases is obtained by combining Boyle`s law, Karl`s law and Gay-Lussac`s law. It shows the relationship between pressure, volume and temperature for a solid mass (quantity) of gas: gases that obey the laws of gas (Charles` law, Boyles` law and universal law of gas) are called ideal gases. The laws of Boyle, Charles and Gay Lussac describe the basic behavior of liquids in terms of volume, pressure and temperature. . PV = constant (If the temperature remains constant, the product of the pressure and volume of a given mass of a gas is constant.) .
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