Corrosion is a process of deterioration and consequent loss of solid metallic materials through an unwanted chemical or electrochemical attack by its environment starting at the surface. The chemical corrosion occurs due to the direct chemical action of the environment (e.g., inorganic liquid) or atmospheric gases as O₂, H₂S , SO₂, halogens and ammonia. The extent of chemical corrosion depends on the chemical affinity of solid metal with the corrosive environment and ability of the reaction product to form protective film on the metal surface. The electrochemical corrosion occurs when a metal is in contact with the conducting liquid or when two dissimilar metals or alloys are dipped partially or completely in a solution. The electrochemical corrosion occurs due to the existence of separate anodic or cathodic areas between which there occurs a flow of current through the conducting solution.  The corrosion always occurs at the anodic areas. The rusting of iron occurs due to corrosion. The electrode reactions in the rusting process are as follows:

Anode: \(Fe \rightarrow Fe^{2+}  +  2e^{-};\) \(E^0 = - 0.44V\)

Cathode: \(O_2  +  2H_2O  +  4e^-  \rightarrow  4OH^-;\) \(E^0 = 1.23 V\)

The overall reaction is

\(Fe  +  O_2  +  H_2O  \rightarrow  Fe^{2+}  +  2OH^- ;\) \(E^0 = 1.67 V\)

The Fe2⁺ and OH⁻ ions combine to form Fe(OH)₂ which is oxidized to Fe(OH)₃ in excess of oxygen. The product formed corresponds to Fe₂O₃.xH₂O. If the supply of oxygen is limited, the corrosion product is black magnetite (Fe₃O₄).

Which of the following cell cannot be recharged?

primary cell

The correct answer is option 3. Primary cells. 

Let us look at the types of cells and their rechargeability: 

1. Fuel Cell

Fuel cells generate electricity through a continuous chemical reaction between a fuel (like hydrogen) and an oxidant (like oxygen). Fuel cells are not recharged in the traditional sense. Instead, they continuously produce electricity as long as fuel and oxidant are supplied. The reaction is not reversible within the cell itself; you need to replenish the fuel externally.

2. Solar Cell

Solar cells (photovoltaic cells) convert light energy into electrical energy through the photovoltaic effect. Solar cells do not store energy themselves but produce electricity when exposed to light. They do not undergo a discharge and recharge cycle.

3. Primary Cell

Primary cells, also known as disposable batteries, generate electrical energy through irreversible chemical reactions. Examples include alkaline batteries and zinc-carbon batteries. Primary cells are designed for a single-use. Once the chemical reactants are depleted, the cell cannot be recharged or reused. The reactions that produce electricity in primary cells are not reversible, so they cannot be restored to their original state by applying an external electrical current.

Primary cells are used in devices where long-term, low-drain power is needed, such as remote controls, flashlights, and some medical devices. The chemical reactions in primary cells are designed to be efficient for one-time use, focusing on cost-effectiveness and long shelf life rather than rechargeability. Example Reaction in an Alkaline Battery:

\(\text{Zn (s)} + 2\text{MnO}_2 (s) + 2\text{H}_2\text{O (l)} \rightarrow \text{Zn(OH)}_2 (s) + 2\text{MnO(OH)} (s)\)

This reaction is not reversible, which means the battery cannot be recharged.

4. Secondary Cell

Secondary cells, or rechargeable batteries, generate electrical energy through reversible chemical reactions. Examples include lithium-ion batteries, nickel-cadmium batteries, and lead-acid batteries. Secondary cells are designed to be recharged and reused multiple times. By applying an external electrical current, the chemical reactions that occur during discharge can be reversed, restoring the reactants to their original state and allowing the battery to be reused.

Secondary cells are used in applications where frequent recharging is necessary, such as in mobile phones, laptops, and electric vehicles. They are designed with materials that can undergo multiple charge and discharge cycles. Example Reaction in a Lithium-Ion Battery:

During Discharge: \(\text{LiC}_6 \rightarrow \text{C}_6 + \text{Li}^+ + e^-\)

During Charge: \(\text{C}_6 + \text{Li}^+ + e^- \rightarrow \text{LiC}_6\)

This reversibility allows the battery to be recharged many times.

Out of the types listed, primary cells cannot be recharged because the chemical reactions they rely on are not reversible. Once the reactants are used up, the cell must be discarded. This is in contrast to secondary cells, which are specifically designed to be recharged and reused.

Therefore, the correct answer is primary cell.