The following data are provided: • Naphthalene: ,

CHEMISTRY · Subjective · A Level · Chemistry · Energetics · Energetics

Problem

The following data are provided: • Naphthalene: ΔHfus=19.0 kJ mol−1\Delta H_{\text{fus}} = 19.0\,\text{kJ mol}^{-1}, ΔHvap=56.5 kJ mol−1\Delta H_{\text{vap}} = 56.5\,\text{kJ mol}^{-1}, molar mass = 128 g mol−1128\,\text{g mol}^{-1} • Benzoic acid: ΔHfus=19.8 kJ mol−1\Delta H_{\text{fus}} = 19.8\,\text{kJ mol}^{-1}, ΔHvap=58.0 kJ mol−1\Delta H_{\text{vap}} = 58.0\,\text{kJ mol}^{-1}, molar mass = 122 g mol−1122\,\text{g mol}^{-1} For a 5.00 g5.00\,\text{g} sample of each substance initially at its melting point, calculate the total energy required to convert the solid completely to vapor (melting followed immediately by vaporization). Which substance requires the greater total energy, and by how many kilojoules?

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