When water is electrolysed, the volume of gas collected over one electrode is double the volume collected over the other. Which gas is collected in double volume, and at which electrode?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Hydrogen, at the cathode
Electrolysis decomposes water: \(\mathrm{2H_2O\rightarrow2H_2+O_2}\), so two volumes of hydrogen form for every one volume of oxygen. Hydrogen collects at the cathode (negative electrode) and oxygen at the anode (positive electrode).