Answer: Protons (H+) are very small and have no electrons, so tunnelling and fast diffusion in water occur via the Grotthuss mechanism.
- A Protons (H+) are very small and have no electrons, so tunnelling and fast diffusion in water occur via the Grotthuss mechanism
- B Proton transfer reactions proceed with highly zero activation energy barrier at any temperature in many documented cases
- C Changing the reaction temperature has little measurable effect on the proton transfer rate according to conventional understanding
- D Such reactions occur quickly mainly because bulk liquid water happens to be present nearby in routine practice overall in most cases
Correct answer: A. Protons (H+) are very small and have no electrons, so tunnelling and fast diffusion in water occur via the Grotthuss mechanism
Explanation: In water, proton transfer occurs via the Grotthuss mechanism: cooperative H-bond network rearrangements relay protons faster than normal diffusion.
Each water molecule's O-H bonds (covalent, solid) can hydrogen-bond (dashed) to neighbouring molecules, forming an extended network responsible for water's unusually high boiling point and density anomaly.
Concept context
The simplest and most abundant element in the universe. Study its unique position in the periodic table, isotopes (protium, deuterium, tritium), properties of water and hydrogen peroxide, and industrial uses.