Question

Covalent bonds in molecules have dissociation energies (D0​) specific to the particular bond. An upper bound for D0​ is known for possible covalent bonds. It's unclear whether continuously adding energy to a system guarantees the breaking of all covalent bonds, or if other physical processes may absorb energy, preventing total homolysis. The central question is whether there exists a temperature above which covalent bonds cannot be maintained substantially. Is there a critical temperature beyond which, for any given mixture of atoms, molecular compounds cannot exist in a substantial way? In other words, is there a temperature threshold at which thermal energy is so high that chemical bonding is practically eliminated? For thermal plasma, how hot does it need to be to eliminate virtually all chemical bonding? Is there a temperature at which the thermal energy is so intense that it surpasses the dissociation energies of virtually all covalent bonds?

Answer 1

There is indeed a threshold temperature beyond which covalent bonds cannot substantially be maintained. The thermal energy at such high temperatures would surpass the dissociation energies for most bonds, leading to a state of thermal plasma where chemical bonding is practically nonexistent.

Step-by-step explanation:

The question asks whether there is a critical temperature beyond which covalent bonds cannot be maintained, effectively eliminating molecular compounds. To answer this, we consider the concept of bond dissociation energy (D0), which is the energy required to break a specific covalent bond. For example, to break a C-H bond, it takes roughly 100 kcal/mol.

Consequently, we infer that if the thermal energy in a system exceeds the bond dissociation energies of the molecules present, those bonds would be broken, leading to dissociation into individual atoms. For hydrogen H2, a molecule known for its strong covalent bond, the dissociation energy is substantial, approximately 436 kJ/mol. However, this bond can be broken at temperatures over 3000 K.

It is implied that at extremely high temperatures, potentially in the range of 30,000 K, the molecular compounds would not exist substantially as the thermal energy would surpass the bond dissociation energies. At such temperatures, a thermal plasma state can be achieved where virtually all chemical bonding is eliminated.