Problem 46 - Advanced Problems in Physical Chemistry for Competitive Examinations

Question

Which is correct about fuel cells? (a) Cell continuously run as long as fuels are supplied. (b) These are more efficient and free from pollution. (c) These are used to provide power and drinking water to astronauts in space programme. (d) All of these

Step-by-Step Solution

Answer

Option (d) 'All of these' is correct.

Step 1: Analyze Option (a)

Assess the validity of the statement that fuel cells will continuously run as long as fuels are supplied. This is true because fuel cells do convert chemical energy from fuels into electricity through a chemical reaction with oxygen or another oxidizing agent. Hence, as long as fuel is available, they can continue to generate power.

Step 2: Examine Option (b)

Evaluate the statement regarding efficiency and pollution. Fuel cells are generally more efficient than traditional combustion-based power systems and produce less pollution, especially since their only by-products are typically heat and water, making this option correct as well.

Step 3: Consider Option (c)

Confirm the accuracy of the statement that fuel cells provide power and drinking water to astronauts. This is correct because, in space programs, fuel cells have been used in spacecraft to generate power and the by-product, which is water, is indeed used for drinking by astronauts.

Step 4: Evaluate Option (d)

Determine if all the given statements about fuel cells are true. Based on the validation of options (a), (b), and (c), all the given statements are correct which makes option (d) the right choice.

Key Concepts

Energy Conversion in Fuel Cells

Fuel cells are remarkable devices that convert chemical energy directly into electrical energy, offering a high level of efficiency. At the heart of a fuel cell is the electrochemical reaction that takes place between a fuel, usually hydrogen, and an oxidant, which is often oxygen. This reaction occurs in two separate electrodes, the anode and the cathode, which are divided by an electrolyte.

The key to this process is the catalyst, typically made of platinum, which facilitates the separation of hydrogen into protons and electrons at the anode. The protons then pass through the electrolyte to the cathode, while the electrons travel through an external circuit, creating electric current. Upon reaching the cathode, electrons reunite with protons and oxygen to produce water as a by-product. The beauty of this energy conversion lies in its cleanliness – the only emissions are water vapor and heat.

Efficiency of Fuel Cells

The efficiency of a fuel cell is a measure of how well it converts the energy in the fuel into electrical energy. In terms of electrical efficiency, fuel cells can outperform traditional combustion engines, which are often subject to energy losses through heat and noise. A fuel cell's efficiency can range from about 40-60%, and can even exceed this range in some applications when waste heat is also utilized in a combined heat and power (CHP) system.

Factors like the type of fuel cell, the quality of the components, and the operating temperature all play a vital role in determining the overall efficiency. For comparison, internal combustion engines generally have an efficiency of about 25-30%. The high efficiency of fuel cells makes them an attractive option for various applications where energy conservation and reducing emissions are crucial.

Applications of Fuel Cells in Space Programs

Fuel cells have a venerable history in space exploration and their role in space programs is critical. They provided the electrical power for NASA's Apollo missions to the moon. Moreover, the water produced as a by-product of the power generation process served a dual purpose as drinking water for astronauts. Since space missions require reliable and efficient sources of power, fuel cells are a natural fit due to their high energy density and efficiency.

Space Shuttle

The Space Shuttle program utilized fuel cells to produce power for onboard systems during missions.

Current and Future Missions

Today, fuel cells are also being considered for long-term space missions, like those to Mars, where resupplying is not feasible. Their reliability, coupled with the ability to also produce necessary water, makes them a pivotal technology for the future of space exploration.