Question

The electrolyte used in $H_2 - O_2$ fuel cell is ________.

• A. aqueous KCl
• B. aqueous KOH
• C. aqueous HCl
• D. aqueous $KNO_3$

Hint:

Remember that "Alkaline Fuel Cells" (AFCs) specifically use aqueous potassium hydroxide as the electrolyte because it has the highest conductivity among the alkali metal hydroxides.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions.
In a standard Hydrogen-Oxygen ($H_2 - O_2$) fuel cell, the electrolyte serves as the medium for the movement of ions between the electrodes.
Step 2: Detailed Explanation:
The most commonly used electrolyte in these cells is a concentrated solution of potassium hydroxide ($KOH$) because it provides high ionic conductivity and facilitates the alkaline medium required for the reaction.
The electrode reactions are:
At Anode: \( 2H_2(g) + 4OH^-(aq) \rightarrow 4H_2O(l) + 4e^- \)
At Cathode: \( O_2(g) + 2H_2O(l) + 4e^- \rightarrow 4OH^-(aq) \)
The hydroxyl ions (\( OH^- \)) are supplied by the aqueous KOH electrolyte.
Step 3: Final Answer:
Therefore, the electrolyte used is aqueous KOH.