Hydrogen gas reacts with chlorine gas to form hydrogen chloride according to the following equation: H₂ + Cl₂ → 2HCl. The bond energies of the relevant bonds are:
- H–H = 436 kJ/mol
- Cl–Cl = 243 kJ/mol
- H–Cl = 431 kJ/mol.
What is the overall enthalpy change?