To determine the enthalpy change for the reaction, we can use the following equation:H_reaction = H_f products - H_f reactants For the given reaction: Na2CO3 s + H2O l 2NaOH s + CO2 g H_f Na2CO3 = -1130 kJ/molH_f H2O = -286 kJ/molH_f NaOH = -425 kJ/molThe enthalpy of formation for CO2 is not given, but we can calculate it using the heat of absorption of CO2 by NaOH pellets:H_absorption = -20.9 kJ/molSince the desorption process is the reverse of the absorption process, the enthalpy of desorption of CO2 is the opposite of the heat of absorption:H_desorption CO2 = 20.9 kJ/molNow we can calculate the enthalpy change for the reaction:H_reaction = [2 H_f NaOH + H_desorption CO2 ] - [H_f Na2CO3 + H_f H2O ]H_reaction = [2 -425 kJ/mol + 20.9 kJ/mol] - [-1130 kJ/mol - 286 kJ/mol]H_reaction = [-850 kJ/mol + 20.9 kJ/mol] - [-1416 kJ/mol]H_reaction = -829.1 kJ/mol + 1416 kJ/molH_reaction = 586.9 kJ/molThe enthalpy change for the reaction Na2CO3 s + H2O l 2NaOH s + CO2 g is 586.9 kJ/mol.