Answer: Electrochemical oxidation of H 2 at anode, reduction of O 2 at cathode, water as byproduct.
- A Electrochemical oxidation of H<sub>2</sub> at anode, reduction of O<sub>2</sub> at cathode, water as byproduct
- B Direct flame combustion of hydrogen gas inside the cell housing in routine practice
- C Controlled nuclear fusion of hydrogen nuclei within the cell overall in most cases
- D Thermal decomposition of hydrogen peroxide releasing oxygen gas under typical conditions
Correct answer: A. Electrochemical oxidation of H<sub>2</sub> at anode, reduction of O<sub>2</sub> at cathode, water as byproduct
Explanation: In a PEM fuel cell: H<sub>2</sub> → 2H+ + 2e- (anode); O<sub>2</sub> + 4H+ + 4e- → 2H<sub>2</sub>O (cathode). Electrical energy from chemical energy without combustion.
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.