To calculate the enthalpy change H for the isomerization of butene-1 to butene-2, we can use Hess's Law. According to Hess's Law, the enthalpy change for a reaction is the same whether it occurs in one step or several steps. In this case, we can consider the combustion of butene-1 and butene-2 as two separate steps.Step 1: Combustion of butene-1Butene-1 + O2 Combustion productsH1 = -2657.7 kJ/molStep 2: Combustion of butene-2Butene-2 + O2 Combustion productsH2 = -2674.4 kJ/molNow, we can use these two steps to calculate the enthalpy change for the isomerization of butene-1 to butene-2:Step 3: Isomerization of butene-1 to butene-2Butene-1 Butene-2H3 = ?According to Hess's Law, the sum of the enthalpy changes for steps 1 and 2 should be equal to the enthalpy change for step 3:H1 + H2 = H3Since we want to find the enthalpy change for the isomerization of butene-1 to butene-2 H3 , we can rearrange the equation:H3 = H2 - H1Now, we can plug in the values for H1 and H2:H3 = -2674.4 kJ/mol - -2657.7 kJ/mol H3 = -16.7 kJ/molSo, the enthalpy change H for the isomerization of butene-1 to butene-2 is -16.7 kJ/mol.