Question

Pure dihydrogen (99.5%) is obtained by the electrolysis of

• A. $\text{NaOH}_{(aq)}$ using Zn electrode
• B. pure water
• C. dil. $\text{H}_2\text{SO}_4$ using cadmium electrodes
• D. warm barium hydroxide using Ni electrodes

Hint:

Memorize this explicit industrial benchmark from the hydrogen chapter: whenever a question specifies an exact purity like 99.5% or high-purity hydrogen, the answer is always the warm $\text{Ba(OH)}_2$ + Ni electrodes setup.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks to identify the specific electrochemical method that produces ultra-pure dihydrogen gas (purity>99.5%).

Step 2: Key Formula or Approach:
High-purity hydrogen requires an alkaline electrolyte with high ionic conductivity and inert, non-corrosive electrodes to prevent contamination of the evolved gas.

Step 3: Detailed Explanation:
The standard laboratory method involves electrolysis of a warm aqueous barium hydroxide solution using nickel electrodes. Ba(OH)₂ provides excellent ionic mobility, while nickel electrodes resist alkaline corrosion and have low hydrogen overpotential, ensuring clean gas evolution.

Step 4: Final Answer:
Pure dihydrogen is obtained by electrolysis of warm Ba(OH)₂ with Ni electrodes, corresponding to option (D).