Intermolecular forces and physical propertiesEdexcel International A Level Chemistry: Mind map

Exam questions on Intermolecular forces and physical properties

1. Alkanes are used as fuels. The boiling temperatures of the first four straight-chain alkanes are: methane 112 K, ethane 184 K, propane 231 K and butane 273 K.
   Predict whether the boiling temperature of pentane is higher or lower than that of butane. Give a reason.2 marks
2. Pentane, 2-methylbutane and 2,2-dimethylpropane are isomers with the molecular formula C₅H₁₂. Pentane has an unbranched chain, 2-methylbutane has one methyl branch and 2,2-dimethylpropane has two methyl branches on the same carbon atom. Their boiling temperatures are 309 K, 301 K and 283 K respectively.
   Explain why pentane has a higher boiling temperature than 2-methylbutane.2 marks
3. Methanol, CH₃OH, and ethane, C₂H₆, each have 18 electrons per molecule. Methanol boils at 338 K and ethane boils at 184 K. Propan-1-ol, CH₃CH₂CH₂OH, and butane, C₄H₁₀, each have 34 electrons per molecule, and ethanol, C₂H₅OH, has 26 electrons per molecule.
   Explain why methanol has a much higher boiling temperature than ethane.3 marks