The behaviour of a real gas is usually depicted by plotting the compressibility factor Z versus P at a constant temperature. At high temperatures and high pressure, Z is usually more than one. This fact can be explained by the van der Waals equation when:
Correct answer: A. The constant 'a' is negligible and not 'b'
- A. The constant 'a' is negligible and not 'b'
- B. The constant 'b' is negligible and not 'a'
- C. Both constants 'a' & 'b' are negligible
- D. Both the constants 'a' & 'b' are not negligible
Explanation
At high pressures, molecules are close together, so the molecular volume (related to 'b') is no longer negligible. At high temperatures, the kinetic energy is high, making the intermolecular attraction forces (related to 'a') negligible. In this case, the repulsive forces dominate, making the gas less compressible than ideal (Z > 1).
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About Gases
Gas behaviour is explained through the kinetic molecular theory and the relationships among pressure, volume and temperature. Work includes STP, Boyle's and Charles's laws, absolute zero, the ideal gas equation, and the distinction between ideal and real gases, especially the effects of intermolecular forces and molecular volume.
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