Question

9. (4 pts.) When refluxing, a mixture of toluene and water is refluxing and condensing in the Hickman still head. A specific mixture of toluene and water will actually boil at a LOWER TEMPERATURE then either pure toluene or pure water. This is the azeotrope mixture, toluene and water can from an azeotrope. The practical consequence of this is that the toluene solvent will always have at least some water in it when it boils, which is how we are able to remove the water from the reaction mixture. Azeotrope mixtures such as these can be understood if the intermolecular forces that hold the molecule together in the liquid form are WEAKER in the mixture than in the pure liquids. Hydrogen bonding is the most important intermolecular force that holds water molecules together in pure water. In the structure(s) shown below, clearly indicate the 10. (2 pts.) In the structure(s) shown below for toluene, state which would be the strongest intermolecular force that holds the toluene molecules together in the liquid phase. 11. (8 pts.) Presumably it is because BOTH of these intermolecular forces are weaker in the mixture that the boiling point of the mixture is lower. For the structures below, state what the strongest intermolecular force is likely to be and BRIEFLY SUGGEST POSSIBLE REASONS why the intermolecular force between the two molecules might be weaker than the intermolecular forces between the pure substances you gave in answer to the previous 2 questions.

Answer 1