Answer :
To calculate the bond energy of HCl, we subtract the total energy released by forming the bonds from the total energy required to break the bonds of the reactants and then divide by the number of moles formed. However, there seems to be a discrepancy in the options provided as none match the calculated energy.Given the options, the correct answer is:A. 245 KJ mol^-1
The question is asking for the bond energy of the hydrogen chloride (HCl) bond based on given bond energies for hydrogen (H-H) and chlorine (Cl-Cl) and the known reaction to form HCl from H2 and Cl2. To find the bond energy per mole of HCl bonds, we can take the energy required to break the bonds in the reactants and subtract the energy released by forming the products.
The energy required to break the H-H bond is 436 kJ/mol, and for the Cl-Cl bond is 243 kJ/mol. Therefore, breaking one mole of each bond requires (436 kJ + 243 kJ) which equals 679 kJ. During the reaction, the formation of two moles of HCl releases energy, which is 2 x 432 kJ: this sums up to 864 kJ released.
The net energy change ( ΔH) can be calculated by the energy released minus the energy required: 864 kJ (released) - 679 kJ (required) = 185 kJ (net release).However, since two moles of HCl are formed, the bond energy per mole of HCl is half of the net energy release. We take 185 kJ and divide by 2 to get approximately 92.5 kJ/mol. The closest value to this, from the provided options, is 154 kJ/mol, which seems to be a typographical or conceptual error in the question or the choices provided.
Given the options, the correct answer is:A. 245 KJ mol^-1
