A 12.0 g sample of benzene, C₆H₆ (molar mass = 78.1 g mol⁻¹), is at its normal melting point of 5.5 °C. Selected thermodynamic data are provided.
ΔH_fus = 9.9 kJ mol⁻¹ ΔH_vap = 30.8 kJ mol⁻¹
(a) Calculate the quantity of heat required to convert the sample from solid to liquid at 5.5 °C.
(b) Calculate the quantity of heat required to convert the *same* sample of liquid benzene at its normal boiling point (80.1 °C) completely into vapor at that temperature.
(c) Determine the ratio of the energy required for vaporization (part b) to the energy required for fusion (part a). Briefly state what this ratio reveals about the relative changes in particle motion and intermolecular forces for the two phase transitions.