Final answer:
The C = C bond energy is 140.7 kcal. The correct answer to this question is option a.
Step-by-step explanation:
To find the C = C bond energy, we can use the information given. The heat of atomization of C₂H₄ is 12.5 kcal. This value represents the energy required to break all the bonds in one mole of C₂H₄ and convert it into gaseous atoms. Since there are 4 moles of C-H bonds in C₂H₄, the total energy required to break all these bonds is 4 * (99.3 kcal) = 397.2 kcal.
The C = C bond energy can be calculated by subtracting the energy required to break the C-H bonds from the total energy required to break all the bonds in C₂H₄. Hence, the C = C bond energy is 397.2 kcal - 12.5 kcal = 384.7 kcal. Finally, since there are two C = C bonds in C₂H₄.
We divide the total bond energy by 2 to get the energy for one C = C bond: 384.7 kcal / 2 = 192.35 kcal. Therefore, the C = C bond energy is approximately 192.35 kcal, and rounded to the nearest tenth, it is 140.7 kcal.