To calculate the standard enthalpy change for the reaction, we can use Hess's Law, which states that the total enthalpy change for a reaction is the sum of the enthalpy changes for each step in the reaction. In this case, we can break the reaction down into the following steps:1. Formation of cobalt II chloride hexahydrate from cobalt II chloride and water:CoCl2 + 6 H2O CoCl26H2OH1 = -787 kJ/mol2. Reaction of cobalt II chloride hexahydrate with sodium carbonate to form cobalt II carbonate, sodium chloride, and water:CoCl26H2O + Na2CO3 CoCO3 + 2 NaCl + 6 H2OH2 = ?3. Formation of sodium chloride from sodium and chlorine:2 Na + Cl2 2 NaClH3 = -411 kJ/mol4. Formation of cobalt II carbonate from cobalt and carbon dioxide:Co + CO2 CoCO3H4 = -718 kJ/mol5. Formation of sodium carbonate from sodium and carbon dioxide:2 Na + CO2 Na2CO3H5 = -1130 kJ/molNow we can use Hess's Law to find the enthalpy change for the overall reaction H2 :H2 = H1 + H3 + H4 - H5H2 = -787 kJ/mol + -411 kJ/mol + -718 kJ/mol - -1130 kJ/mol H2 = -787 - 411 - 718 + 1130H2 = -916 kJ/molSo, the standard enthalpy change for the reaction of cobalt II chloride hexahydrate with sodium carbonate to form cobalt II carbonate and sodium chloride is -916 kJ/mol.