To calculate the enthalpy change of isomerization of butene-1 to cis-butene-2, we can use Hess's Law. According to Hess's Law, the enthalpy change of a reaction is the same whether it occurs in one step or several steps. In this case, we can use the enthalpy of combustion values to determine the enthalpy change of isomerization.The reactions are as follows:1. Isomerization: butene-1 cis-butene-2 H = ? 2. Combustion of butene-1: butene-1 + O CO + HO H = -2657 kJ/mol 3. Combustion of cis-butene-2: cis-butene-2 + O CO + HO H = -2670 kJ/mol We can use the combustion reactions to create a pathway for the isomerization reaction:1. Combustion of butene-1 reverse : CO + HO butene-1 + O H = +2657 kJ/mol 2. Combustion of cis-butene-2: cis-butene-2 + O CO + HO H = -2670 kJ/mol Now, we can add these two reactions to get the isomerization reaction:CO + HO butene-1 + O H = +2657 kJ/mol butene-1 cis-butene-2 + O H = -2670 kJ/mol ----------------------------------------------CO + HO cis-butene-2 + O H = -13 kJ/mol Thus, the enthalpy change of isomerization of butene-1 to cis-butene-2 at 25C and 1 atm is -13 kJ/mol.