Read the following passage and answer the next five questions based on it:

Battery or cell converts chemical energy of the redox reaction to electrical energy. In fuel cell (a galvanic cell), the chemical energy of combustion of fuels like \(H_2\), ethanol, etc, are directly converted to electrical energy. In a fuel cell, \(H_2\) and \(O_2\) react to produce electricity, where \(H_2\) gas is oxidized at anode and oxygen is reduced at cathode and the reactions involved are:

Anode Reaction :\(H_2 + 2OH^- \longrightarrow 2H_2O + 2e^-\)

Cathode reaction: \(O_2 + 2H_2O + 4e^- \longrightarrow 4OH^-\)

\(67.2 L\) of \(H_2\) at STP reacts in \(15 \) minutes

The source of electrical energy on the Apollo moon-flight was:

\(H_2-O_2\) fuel cell

The correct answer is option 4. \(H_2-O_2\) fuel cell.

The Apollo moon missions, conducted by NASA from 1969 to 1972, utilized \(H_2-O_2\) fuel cells as their primary source of electrical energy. Here’s a detailed explanation of why and how these fuel cells were used:

Why \(H_2-O_2\) Fuel Cells Were Used

1. Efficiency and Reliability:

High Energy Density: \(H_2-O_2\) fuel cells have a high energy density, meaning they can produce a large amount of energy relative to their size and weight. This was crucial for space missions where every kilogram mattered.

Reliability: Fuel cells provided a continuous and reliable source of electricity, essential for the critical systems on the spacecraft, including life support, navigation, and communication.

2. Byproducts:

Water Production: One of the byproducts of the fuel cell reaction is water (H₂O), which was used by the astronauts for drinking and other purposes. This reduced the need to carry large quantities of water from Earth.

3. Safety:

Controlled Reaction: Unlike chemical batteries or generators, fuel cells do not have moving parts and are less prone to mechanical failure. This increased the safety and reliability of the power source.

How \(H_2-O_2\) Fuel Cells Worked

1. Chemical Reaction:

Anode Reaction: At the anode, hydrogen gas (H₂) is oxidized.

\(H_2 + 2OH^- \longrightarrow 2H_2O + 2e^-\)

Cathode Reaction: At the cathode, oxygen gas (O₂) is reduced.

\(O_2 + 2H_2O + 4e^- \longrightarrow 4OH^-\)

2. Energy Production:

Electrons Flow: The electrons produced at the anode flow through an external circuit to the cathode, creating an electric current that powers the spacecraft’s systems.

Heat Management: The reaction also produces heat, which was managed through the spacecraft’s thermal control systems.

3. Integration in Apollo Missions:

Power Management: The fuel cells were integrated with the spacecraft's power management systems to ensure a stable and regulated supply of electricity.

Redundancy: Multiple fuel cells were used to provide redundancy and ensure that power was always available, even if one cell failed.

The \(H_2-O_2\) fuel cells were a critical component of the Apollo missions, providing a reliable, efficient, and safe source of electrical energy. They not only powered the spacecraft but also contributed to the astronauts' life support by supplying water. The successful use of fuel cells in the Apollo program demonstrated their viability for space exploration, paving the way for their use in other missions and applications.