An ideal gas is an imaginary substance that obeys the relation pV = RT.
CONCEPT OF IDEAL AND REAL GASES
1. Ideal gas:
An ideal gas is an imaginary substance that obeys the relation pV = RT. So, the state equation is also known as ideal gas equation. At low pressure and high temperature, the density of a gas decreases. At that time, the gas behaves as an ideal gas. A factor is introduced to account the deviation of ideal gas behaviour known as compressibility factor. It is a measure of the deviation of ideal gas behaviour.
2. Real gas:
At high pressures, the gases start to deviate from ideal gas behaviour. So, the deviation should be accounted. For accounting this deviation, a factor called compressibility is introduced. The state equation for real gases is given by
pV = ZRT …..(1.26)
where
Z = Compressibility factor
⸫ Compressibility factor,
Z = pV / RT …..(1.27)
Compressibility factor can also be expressed by
Z = vActual / vIdeal ... (1.28)
where
vActual ⇒ Specific volume of real gases
vIdeal ⇒ Specific volume of ideal gases
For ideal gases, Z = 1. But, for real gases, Z is greater than or less than unity. The graph is plotted between pressure, temperature and compressibility to account deviation of ideal gas behaviour.
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