Calculation of enthalpy changes of reaction using bond energies
2 marks · EasyThe reaction below occurs: Bond energies (kJ/mol): HI: 299, H–H: 436, I–I: 151 Calculate the enthalpy change (ΔH) for the reaction.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
-87 kJ/mol (±2)
Must show: Shows total bond breaking energy and total bond making energy
Also accept: -86 kJ/mol
Common mistakes: Incorrect sign; Not multiplying HI energy by 2
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Shows correct calculation for both bonds broken and bonds made.
A1 · 1 mark · Gives final answer with sign, (–87 kJ/mol) or within tolerance.
Worked solution