Question: how much energy is required to break the bond in h2?
Answer: In water's hydrogen bonds, the hydrogen atom is covalently attached to the oxygen of a water molecule (492.2145 kJ ˣ mol-1 [350]) but has (optimally) an additional attraction (about 23.3 kJ mol-1 [168]. This is the energy (ΔH) required for breaking the bond and completely separating the atoms.