Question

Calculate the enthalpy change for the isomerization of But-1-ene to But-2-ene using the given bond enthalpies: C-C single bond (347 kJ/mol), C-H bond (413 kJ/mol), C=C double bond (611 kJ/mol), and the enthalpy of formation of But-1-ene (-4.8 kcal/mol) and But-2-ene (-0.9 kcal/mol).

Answer 1

To calculate the enthalpy change for the isomerization of But-1-ene to But-2-ene, we can use the bond enthalpies and the enthalpy of formation values given.First, let's convert the enthalpy of formation values from kcal/mol to kJ/mol:-4.8 kcal/mol * 4.184 kJ/kcal = -20.0832 kJ/mol  But-1-ene -0.9 kcal/mol * 4.184 kJ/kcal = -3.7656 kJ/mol  But-2-ene Now, let's analyze the bonds in both molecules:But-1-ene: 1 C=C bond, 3 C-C bonds, and 8 C-H bondsBut-2-ene: 1 C=C bond, 3 C-C bonds, and 8 C-H bondsSince the number of each bond type is the same in both molecules, the bond enthalpies will cancel each other out when calculating the enthalpy change. Therefore, we can use the enthalpy of formation values to calculate the enthalpy change for the isomerization:H = H_f  But-2-ene  - H_f  But-1-ene H =  -3.7656 kJ/mol  -  -20.0832 kJ/mol H = 16.3176 kJ/molThe enthalpy change for the isomerization of But-1-ene to But-2-ene is 16.32 kJ/mol  rounded to two decimal places .