Moderate

In the van der Waals equation (P + n2a / v2) (v - nb) = nRT which of the following statement is not true ?

Correct answer: C. at high densities the equation reduces to the ideal gas law

  • A. n2a/v correct for the intermolecular forces.
  • B. nb correct for the volume occupied by gas molecules.
  • C. at high densities the equation reduces to the ideal gas law
  • D. all of the above statements are correct.

Explanation

In the van der Waals equation, the pressure correction n2a/v2 accounts for intermolecular attraction and the volume correction nb accounts for the finite molecular volume. At high density, real-gas effects become more important, so the equation does not reduce to the ideal gas law; ideal behaviour is approached at low pressure or low density. The likely mistake is choosing d by accepting all statements without checking the density condition.

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About Real and Ideal Gases

An ideal gas is modelled as particles with negligible volume and no intermolecular attraction, obeying Boyle's, Charles's and Avogadro's laws through PV = nRT. Real gases deviate from this behaviour, especially at high pressure and low temperature, because particle volume and attractive forces matter; the van der Waals equation explains these corrections.

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