(Li, Na, K)OH hydration bonding thermodynamics: Solution self-heating

Highlights: • YOH dissolves into a Y⁺ and a HO⁻ with three electron lone pairs ":" and a shorter H–O bond. • The Y⁺ shortens its hydrating H–O bonds and lengthens the other O:H parts cooperatively. • The excessive ":" forms an O:⇔:O compressor that lengthens its contacting H–O bond. • Energy difference between H–O elongation and H–O contraction heats up the solution. The resultant energy of solvent H–O bond exothermic elongation by O:⇔:O repulsion, featured at < 3100 cm⁻¹, and the solute H–O bond endothermic contraction by bond-order-deficiency, at 3610 cm⁻¹, heats up the (Li, Na, K)OH solutions. The solution temperature increases linearly with the number fraction of the ordinary O:H–O bonds transiting into their hydration states. The elongated H–O bond emits >150% the O:H cohesive energy of 0.095 eV that caps the energy dissipating by molecular motion, thermal fluctuation, diffusion, and even evaporation. Therefore, the intramolecular H–O bond relaxation dictates the OH⁻ solvation bonding thermodynamics and the performance of basic solutions.