To calculate the standard enthalpy change for the phase transition reaction of solid carbon dioxide dry ice at -78.5C to gaseous carbon dioxide at 1 atm and 25C, we need to consider the following steps:1. Heating solid CO2 from -78.5C to its sublimation point -56.6C 2. Sublimation of solid CO2 to gaseous CO23. Heating gaseous CO2 from -56.6C to 25CStep 1: Heating solid CO2 from -78.5C to its sublimation point -56.6C To calculate the enthalpy change for this step, we need the heat capacity of solid CO2. The heat capacity of solid CO2 is approximately 37.135 J/molK.H1 = heat capacity TH1 = 37.135 J/molK -56.6C - -78.5C H1 = 37.135 J/molK 21.9 KH1 = 812.56 J/molH1 = 0.81256 kJ/molStep 2: Sublimation of solid CO2 to gaseous CO2The standard enthalpy of sublimation is equal to the sum of the standard enthalpy of fusion and the standard enthalpy of vaporization.H_sublimation = H_fusion + H_vaporizationH_sublimation = 8.4 kJ/mol + 22.1 kJ/molH_sublimation = 30.5 kJ/molStep 3: Heating gaseous CO2 from -56.6C to 25CTo calculate the enthalpy change for this step, we need the heat capacity of gaseous CO2. The heat capacity of gaseous CO2 is approximately 36.94 J/molK.H3 = heat capacity TH3 = 36.94 J/molK 25C - -56.6C H3 = 36.94 J/molK 81.6 KH3 = 3015.024 J/molH3 = 3.015024 kJ/molNow, we can calculate the total standard enthalpy change for the phase transition:H_total = H1 + H_sublimation + H3H_total = 0.81256 kJ/mol + 30.5 kJ/mol + 3.015024 kJ/molH_total = 34.327584 kJ/molThe standard enthalpy change for the phase transition reaction of solid carbon dioxide dry ice at -78.5C to gaseous carbon dioxide at 1 atm and 25C is approximately 34.33 kJ/mol.