Chemistry 9701 · AS & A Level · States of matter

States of matter — practice question

Ethanol has a boiling point of $78^\circ\text{C}$. When the pressure is $101\ \text{kPa}$ and the temperature is $79^\circ\text{C}$, ethanol vapour does not obey the gas equation $pV = nRT$ exactly. What is the reason for this?

  • AEthanol vapour is in equilibrium with ethanol liquid at $79^\circ\text{C}$.
  • BThere are intermolecular forces between the molecules of ethanol vapour.
  • CThe vapourisation of ethanol liquid is an endothermic process.
  • DVapours will not obey the gas equation perfectly at such a low pressure.

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