A molecular solid (substance A) has and at 1 atm

CHEMISTRY · Subjective · A Level · Chemistry · Bonding · Bonding

Problem

A molecular solid (substance A) has ΔHfus=4.0 kJ mol−1\Delta H_{\text{fus}} = 4.0\,\text{kJ}\,\text{mol}^{-1} and ΔHvap=25 kJ mol−1\Delta H_{\text{vap}} = 25\,\text{kJ}\,\text{mol}^{-1} at 1 atm. A second molecular solid (substance B) capable of hydrogen bonding has ΔHfus=7.5 kJ mol−1\Delta H_{\text{fus}} = 7.5\,\text{kJ}\,\text{mol}^{-1} and ΔHvap=53 kJ mol−1\Delta H_{\text{vap}} = 53\,\text{kJ}\,\text{mol}^{-1} at 1 atm. When each solid is placed in a sealed container at 0.20 atm and warmed from −10 °C, which substance is more likely to undergo sublimation before melting, and why?

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