First, we need to determine the number of moles of CO2 in 25 grams of dry ice. The molecular weight of CO2 is 12.01 g/mol for carbon + 2 * 16.00 g/mol for oxygen = 44.01 g/mol.Now, we can calculate the number of moles in 25 grams of dry ice:moles = mass / molecular weightmoles = 25 g / 44.01 g/mol = 0.568 molesNext, we can use the heat of sublimation to calculate the heat energy required to sublime the dry ice:heat energy = moles * heat of sublimationheat energy = 0.568 moles * 573 kJ/mol = 325.5 kJTherefore, the heat energy required to sublime 25 grams of dry ice at -78.5 C is approximately 325.5 kJ.