Comprehension:
Electrolysis
In the electrolysis process, the nature of material being electrolyzed, and the electrodes nature are the important factors in predicting the products of electrolysis. The electrode material, whether acting as a source or sink or itself, is not inert will also decides the nature of the product of the electrolysis. The standard electrode potentials of the various oxidizing and reducing species present in the electrolytic mixture also decides the product of electrolysis. The voltage applied also decides the product of electrolysis since some of the reactions which are feasible are so slow kinetically that they are not seem to take place at lower voltage. The quantitative aspects of electrolysis was described by Faraday law of electrolysis.
What is observed during the electrolysis of the NaCl(s)?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → No electrode reaction
Electrolysis needs mobile ions that can move to the electrodes and carry the current. In an ionic compound, the ions become free to move only when the compound is melted or dissolved in water.
In solid NaCl, the \( \ce{Na^{+}} \) and \( \ce{Cl^{-}} \) ions are held in fixed positions in the crystal lattice by strong electrostatic forces. They cannot move, so solid NaCl does not conduct electricity. No current flows through it, and no electrode reaction takes place.
Why the other options are incorrect
Option (1) Sodium at cathode — Incorrect. This happens in the electrolysis of molten (fused) NaCl, where \( \ce{Na^{+}} \) ions are free to move: \( \ce{Na^+ + e^- -> Na} \)
Option (2) Chlorine at anode — Incorrect. This happens with molten or aqueous NaCl, where \( \ce{Cl^{-}} \) ions reach the anode: \( \ce{2Cl^- -> Cl2 + 2e^-} \)
Option (3) Hydrogen gas at cathode — Incorrect. This happens with aqueous NaCl, where water is reduced; solid NaCl contains no water.