Batteries, Corrosion, and Fuel Cells

Identify whether the system stores reactants inside the cell or receives reactants continuously. Decide whether the reaction is reversible for recharging. For corrosion, locate anodic metal dissolution and cathodic oxygen reduction. Add prevention logic such as barrier coating, galvanisation, or cathodic protection when asked.

A comparison chart is more useful than a full apparatus diagram: primary cell, secondary cell, fuel cell, and corrosion should be compared by reactants, rechargeability, electrode process, and product.

A common wrong answer is calling a fuel cell rechargeable in the same sense as a secondary battery, instead of stating that it works with continuous external reactant supply.

Batteries and fuel cells are electrochemical devices that supply electrical energy through redox reactions, while corrosion is an unwanted electrochemical oxidation process of metals.

Batteries and fuel cells are electrochemical devices that supply electrical energy through redox reactions, while corrosion is an unwanted electrochemical oxidation process of metals. Fuel cell pattern: fuel is oxidised at anode and oxidant is reduced at cathode. Corrosion pattern for iron: anodic region Fe → Fe₂⁺ + 2e-; cathodic oxygen reduction occurs in moist conditions, leading eventually to hydrated iron oxide. Battery classification rule: primary cells are single-use in normal operation; secondary cells are rechargeable. In a hydrogen-oxygen fuel cell, hydrogen is oxidised and oxygen is reduced, producing water and electrical energy. In rusting, iron is oxidised to iron ions, which ultimately form hydrated iron oxide.

Primary batteries are not conveniently rechargeable, while secondary batteries can be recharged by reversing the cell reaction. The Leclanche cell and mercury cell are common primary examples. Lead storage and nickel-cadmium cells are secondary examples. A hydrogen-oxygen fuel cell continuously converts the chemical energy of hydrogen and oxygen into electrical energy as long as reactants are supplied. Corrosion, such as rusting of iron, occurs through small electrochemical cells formed on the metal surface in the presence of oxygen and moisture. Fuel cell pattern: fuel is oxidised at anode and oxidant is reduced at cathode. Corrosion pattern for iron: anodic region Fe → Fe₂⁺ + 2e-; cathodic oxygen reduction occurs in moist conditions, leading eventually to hydrated iron oxide. Battery classification rule: primary cells are single-use in normal operation; secondary cells are rechargeable. Classify lead storage battery and H2-O2 fuel cell. A lead storage battery is a secondary battery because it can be recharged by reversing the reaction using external current. A hydrogen-oxygen fuel cell is not simply a stored-charge battery; it requires continuous supply of hydrogen and oxygen and forms water as product. CBSE questions often ask differences between primary and secondary batteries, reactions in lead storage battery or fuel cell, advantages of fuel cells, conditions for corrosion, and methods to prevent rusting. A common wrong answer is calling a fuel cell rechargeable in the same sense as a secondary battery, instead of stating that it works with continuous external reactant supply.