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Question #44772
The Question
A modified \ce{H2-O2} fuel cell operates at using a dual-membrane system that creates an internal concentration gradient. The anode compartment interfaces with a weak polymeric acid membrane (effective monomeric concentration , acid dissociation constant ). The cathode compartment interfaces with a fully dissociated strong acid membrane (). Both \ce{H2} and \ce{O2} gases are supplied at . Given the standard cell potential , the standard enthalpy of combustion of \ce{H2(g)} to \ce{H2O(l)} as , and Faraday's constant . Assuming at , what is the theoretical thermodynamic efficiency () of this modified fuel cell?
Options
- A.
89.87%
- B.
82.00%
- C.
85.93%
- D.
74.13%
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Mechanism_Trap
Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.
Concepts Behind This Question
Fuel Cell Efficiency|Concentration Cells|Degree of Dissociation (Alpha)
Why This Question Is Tricky
Common Mistakes
This problem tests the intersection of electrochemistry (fuel cells/concentration cells) and ionic equilibrium.
The 'Hidden Variable' is the degree of dissociation () of the weak acid membrane.
Students often blindly plug the analytical concentration () into the Nernst equation, assuming ideal behavior or full dissociation (), which leads to an incorrect of and an efficiency of .
By forcing the calculation of actual proton activity (), the problem highlights the thermodynamic reality of polymer electrolyte membranes where partial dissociation dictates the effective charge carrier concentration.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Electrochemistry - Class 12 |
| Concept | Fuel Cell Efficiency |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |