Question

Which gases are produced at the cathode and anode during the electrolysis of acidulated water?

Hint:

Remember the mnemonic "CROA" - Cathode Reduction, Oxidation Anode. Hydrogen ions reduce to gas at the cathode.

Answer 1

Step 1: Understanding the Concept:
Electrolysis is the process of using electrical energy to drive a non-spontaneous chemical reaction. Water decomposes into hydrogen and oxygen.

Step 2: Detailed Explanation:
In acidulated water, the ions present are mainly \(\text{H}^+\) (from water and acid) and \(\text{OH}^-\) (from water) along with anions from the acid (like \(\text{SO}_4^{2-}\)).
During electrolysis:
1. At the Cathode (negative electrode): Positively charged Hydrogen ions (\(\text{H}^+\)) are attracted. They gain electrons (reduction) to form Hydrogen gas (\(\text{H}_2\)).
Equation: \(2\text{H}^+ + 2\text{e}^- \rightarrow \text{H}_2 \uparrow\)
2. At the Anode (positive electrode): Negatively charged Hydroxide ions (\(\text{OH}^-\)) are attracted and lose electrons (oxidation) to form Oxygen gas (\(\text{O}_2\)) and water.
Equation: \(4\text{OH}^- \rightarrow 2\text{H}_2\text{O} + \text{O}_2 \uparrow + 4\text{e}^-\)

Step 3: Final Answer:
Hydrogen is produced at the cathode, and Oxygen is produced at the anode.