Answer Happy

Question A1 Total for Question A1: [15 marks] Consider the line structure for caffeine, shown below, which has a solubility of 2 g/100 mL in cold water: (a) Redraw this line structure in your answer booklet and annotate it to indicate the location(s) of all the possible lone pairs on this structure. Identify any functional groups that are able to form hydrogen bonds with water molecules. Draw a Lewis structure of a water molecule interacting with each group to illustrate the orientation of the hydrogen bond(s). [4 marks) (b) Caffeine has a solubility of 15 g/100 ml in chloroform at 298 K. Explain why this molecule is more soluble in chloroform than in water at this temperature. [2 marks]
(c) Use the Lennard-Jones (6,12) parameters that have been provided in the table below to draw a labelled potential energy diagram showing the interactions between: (i) a pair of CH3Cl molecules and (ii) between a pair of CCl4 molecules. Molecule ɛ (kJ mol-1) o (nm) CH3CI 855.0 337.5 CCl4 327.0 588.0 [5 marks] (d) Contrast the relative magnitudes in energy and distances of separation for the interaction between two CH3Cl molecules compared to that for two CCl4 molecules. Explain the difference for: (i) the separation distance when the potential energy is zero (o) and (ii) the strength of interaction at the equilibrium separation distance (€) in terms of molecular structure. [4 marks]