11.   The standard molar enthalpy of fusion is a measure of the energy needed to overcome the forces of attraction that exist between particles in the solid state.

12.   Similarly, the standard molar enthalpy of vaporisation is a measure of the energy needed to overcome the forces of attraction that exist between particles in the liquid state.

13.   SOLUTION The molar enthalpy of combustion of methanol is given by The negative sign is required since combustion is exothermic.

14.   The standard molar enthalpy of formation of an element is zero and so the standard molar enthalpy of formation of oxygen need not be included in the above expression.

15.   Experimental evidence for the consistency of bond enthalpies over a number of compounds is provided by the standard molar enthalpies of combustion of alkanes in their homologous series.

16.   The calculated standard molar enthalpy of hydrogenation of this compound is virtually the same as that calculated for ethene.