Bond
Bond Energy
H-H
432
CI-CI
239
H-CI
427
2:26
• I LTE (36)
Mark as Complete
Use the table to answer the question:
Explain how you would calculate the total change in bond energy for the reaction H2 + Cl2 -> 2HCl. How would you know it the reaction was endothermic or exothermic? State your answer in 3-5 sentences.
To calculate the total change in bond energy for the reaction H2 + Cl2 -> 2HCl, you need to add up the bond energies of the bonds broken and subtract the sum of the bond energies of the bonds formed.
In this reaction, you need to break one H-H bond (432 kJ/mol) and one Cl-Cl bond (239 kJ/mol), while you form two H-Cl bonds. The energy released in the formation of two H-Cl bonds is 2 x (427 kJ/mol) = 854 kJ/mol.
To calculate the total change in bond energy, you would subtract the energy required to break the bonds (432 kJ/mol + 239 kJ/mol) from the energy released in the formation of new bonds (854 kJ/mol).
If the total change in bond energy is positive, then the reaction is endothermic, meaning it requires energy input. If the total change in bond energy is negative, then the reaction is exothermic, meaning it releases energy. In this case, you would need to compare the energy released in the formation of H-Cl bonds (854 kJ/mol) with the energy required to break H-H and Cl-Cl bonds (432 kJ/mol + 239 kJ/mol) to determine if the reaction is endothermic or exothermic.