Concept:In electrolysis of dilute hydrochloric acid, the anode oxidises water instead of chloride ions because the chloride ion concentration is very low.
Explanation:At the anode, oxidation always occurs.
The solution contains
H+ ions,
Cl− ions, and water molecules.
Since the acid is dilute,
Cl− ions are present only in small amounts.
Therefore, water molecules lose electrons in preference to chloride ions.
The anode half-reaction is:
2H2O(l)→O2(g)+4H+(aq)+4e−This reaction clearly produces oxygen gas.
Chlorine gas would be liberated only when concentrated hydrochloric acid is used.
Answer:A. Oxygen gas is given off