The correct answer is: B. water is neither formed nor absorbed.
A nickel-iron cell is a type of secondary cell, also known as a rechargeable battery. It is a type of alkaline battery that uses nickel hydroxide and iron as its active materials. The cell has a long life and is resistant to overcharging and deep discharge.
During the charging and discharging of a nickel-iron cell, water is neither formed nor absorbed. The cell uses a chemical reaction to store and release energy. When the cell is charged, the nickel hydroxide is converted to nickel oxide. When the cell is discharged, the nickel oxide is converted back to nickel hydroxide. This reaction does not involve the formation or absorption of water.
The other options are incorrect for the following reasons:
- Option A: Corrosive fumes are not produced during the charging and discharging of a nickel-iron cell.
- Option C: Nickel hydroxide is split during the charging and discharging of a nickel-iron cell. The nickel hydroxide is converted to nickel oxide during charging and back to nickel hydroxide during discharging.
- Option D: The e.m.f. of a nickel-iron cell changes during the charging and discharging process. The e.m.f. is higher during charging and lower during discharging.