A-LevelChemistryStates of matter9701/12 · May/June 2013 · Q71 Mark

Ethanol has a boiling point of 78°C. At 101 kPa and 79°C ethanol vapour does not perfectly obey the gas equation pV = nRT. What is the reason for this?

AEthanol vapour is in equilibrium with ethanol liquid at 79°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.

✓ Correct answer

B: There are intermolecular forces between the molecules of ethanol vapour.

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Topic: States of matter, A-Level Chemistry (syllabus 9701). Multiple choice, 1 mark.
Source: A-Level Chemistry, May/June 2013 Paper 1 Variant 2, question 7.

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