To calculate the heat required to sublime 25 grams of dry ice, we will use the following formula:q = n * H_subwhere q is the heat required, n is the number of moles of the substance, and H_sub is the enthalpy of sublimation.First, we need to find the number of moles n of CO2. The molar mass of CO2 is approximately 44.01 g/mol 12.01 g/mol for C and 16.00 g/mol for each O .n = mass / molar massn = 25 g / 44.01 g/moln 0.568 molesNow we can calculate the heat required q :q = n * H_subq = 0.568 moles * 25.2 kJ/molq 14.32 kJTherefore, the heat required to sublime 25 grams of dry ice at -78.5 C is approximately 14.32 kJ.