Read the following passage given below and answer the question.

Production of electricity by thermal plants is not very efficient method. It is now possible to make cells in which reactants are fed continuously to the electrodes and products are also removed continuously. One of the most successful fuel cells is hydrogen fuel cell.

Hydrogen fuel cell is an:

electrochemical cell

The correct answer is option 1. electrochemical cell.

A hydrogen fuel cell is classified as an electrochemical cell because it generates electricity through a chemical reaction between hydrogen and oxygen. Let us dive into an explanation of the given options to understand why option 1 is correct.

1. Electrochemical Cell (Correct Answer)

An electrochemical cell is a device that converts chemical energy into electrical energy through redox (reduction-oxidation) reactions. In the case of a hydrogen fuel cell, the chemical reaction between hydrogen and oxygen produces electricity, water, and heat. Here's how it works:

At the anode (negative electrode):

Hydrogen gas (H₂) is supplied to the anode, where it is split into protons (H⁺) and electrons (e⁻). This is an oxidation reaction where hydrogen loses electrons:

\(H_2 \longrightarrow 2H^+ + 2e^-\)

The electrons travel through an external circuit, creating an electric current.

At the cathode (positive electrode):

Oxygen (O₂) is supplied to the cathode. It combines with the electrons (which come through the external circuit) and protons (which travel through the electrolyte) to form water (H₂O). This is a reduction reaction:

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

Overall reaction:

\(2H_2 + O_2 \longrightarrow 2H_2O + \text{electricity + heat}\)

The reaction is spontaneous, meaning no external power is needed to drive it. The fuel cell efficiently converts the chemical energy of hydrogen into electrical energy with water as the only by-product.

This is the reason hydrogen fuel cells are classified as electrochemical cells—because they directly produce electricity through a chemical process.

2. Electrolytic Cell (Incorrect)

An electrolytic cell works in the opposite way to an electrochemical cell. In an electrolytic cell, electrical energy is used to drive a non-spontaneous chemical reaction. A common example of an electrolytic process is electrolysis, where electricity is applied to water to split it into hydrogen and oxygen.

A hydrogen fuel cell does not require an external power source to run. Instead, it generates electricity through the spontaneous reaction of hydrogen and oxygen, so it is not an electrolytic cell.

3. Can be both electrochemical and electrolytic cell (Incorrect)

A device cannot be both an electrochemical and an electrolytic cell at the same time, as they function in opposite ways:

An electrochemical cell converts chemical energy into electrical energy (spontaneous reaction). An electrolytic cell uses electrical energy to force a chemical reaction (non-spontaneous reaction).

Since a hydrogen fuel cell generates electricity rather than consuming it to drive a reaction, it functions purely as an electrochemical cell, not both.

4. Neither electrochemical nor electrolytic cell (Incorrect)

This option is incorrect because hydrogen fuel cells are indeed a type of electrochemical cell. They are not "neither" since they fit clearly within the definition of an electrochemical device.

Summary:

A hydrogen fuel cell is an electrochemical cell that generates electricity from the reaction of hydrogen and oxygen. It is not an electrolytic cell, which requires electricity to drive a chemical reaction. Therefore, the correct answer is option 1: Electrochemical cell.