The heat of sublimation is the amount of heat required to convert a substance from its solid phase directly to its gas phase without passing through the liquid phase. In the case of carbon dioxide, we are given the enthalpy of fusion H_fusion and the enthalpy of vaporization H_vaporization .To calculate the heat of sublimation H_sublimation , we can simply add the enthalpy of fusion and the enthalpy of vaporization:H_sublimation = H_fusion + H_vaporizationH_sublimation = 8.44 kJ/mol + 25.2 kJ/molH_sublimation = 33.64 kJ/molSo, the heat of sublimation of solid carbon dioxide CO2 is 33.64 kJ/mol.