Question

What is the maximum work that can be obtained from a hydrogen-oxygen fuel cell at standard conditions that produces 1.00 kg of water at 25°C? Why do we say that this is the maximum work that can be obtained? What are the advantages and disadvantages of using fuel cells rather than the corresponding combustion reactions to produce electricity?

Short answer

The maximum work that can be obtained from a hydrogen-oxygen fuel cell at standard conditions that produces 1.00 kg of water at 25°C will be -13167 kJ. The work cannot exceed the amount of free energy change hence, the maximum work cannot be greater than this. Advantages include efficiency, smaller size and disadvantages include cost inefficiency, difficulty in storage in cars.

Step-by-step solution

Evaluating the maximum work

Reaction in fuel cell:

$2{\mathrm{H}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

$\begin{array}{rcl}& & \mathrm{\Delta }\text{G = 474 kJ/mol}\\ & & {\text{For, 1000g ofH}}_{\text{2}}\text{O}\\ & & \mathrm{\Delta }\text{G = -}\frac{\text{474kJ}}{\text{36g}}\times \text{1000g}\\ & & \text{= - 13167kJ}\end{array}$

Hence,the maximum work that can be obtained from a hydrogen-oxygen fuel cell at standard conditions that produces 1.00 kg of water at 25°C will be -13167 kJ.

Maximum amount of work

The maximum work done can be this becausethe work cannot exceed the amount of free energy change.

Advantages and disadvantages of using fuel cells

Advantages: Fuel cells are more efficient in terms of converting chemical energy into electrical energy. they are also smaller in size hence mobile.

Disadvantages: They are very costly. they are not so long-lasting. And they have hydrogen at room temperature, hence, they are difficult to store in a car.