________________
(b)
Satish K. Gupta, op. cit. Pages 212-216 (Voltaic Cell, Daniel Csu, Lechanche Cell) "In voltaic cell, for each Zn+ ion so produced, two electrons (2 e-) are left on the zinc rod. As more and more Za+ ions enter the electrolyte, the zinc rod becomes more and more negative. Also, the concentration of Za+ ions in the electrolyte goes on increasing. The H+ drift to the copper rod. On reaching the copper rod, the H+ ions extract electrons from the rod and form neutral hydrogen atoms. Asa result of it copper rod acquires positive charge. As more and more H+ ions ions discharge at the copper rod, it becomes more and more positive. Due to positive charges building up on copper rod and negative charge on the zinc rod, the potential difference between the two rods goes on increasing. It continues, till the potential gradient along the electrolyte between copper and zinc rod just restricts the drift of H+ ions to the copper rod.
Daniel Cell
It was developed by Daniel in the year 1836.
Construction. It consists of a copper vessel containing copper sulphate (CuSO) solution. The copper vessel itself acts as the positive pole of the cell, Inside the CuSO, solution, a porus pot containing an amalgamated zinc rod and dilute H2SO, acid is placed. Whereas the porus pot prevents the dilute H2SO, and the CuSO, solution from mixing with each other, it allows the H+ ions produced in the porous pot to diffuse through its walls into the CuSO, solution. The amalgamated zinc rod is used in order to avoid the defect of local action from occuring in the cell. The amalgamated zinc rod acts as the negative role of the cell and both the CuSO, solution and dil, H2SO, serve as the electrolyte. However, the CuSO, solution serves as depolariser also.
When the cell functions, the concentration of CuSO, solution falls. In order to keep the concentrate of CuSO, solution constant, the crystals of CuSO, are placed on the perforated shelf provided along walls of the copper vessel.
Action. Inside the porus pot, the dilute H,SO, acid disociates into H+ and SO, ions. As them rod is dipping inside the dilute H2SO acid, some of the zinc atoms go into the solution as Zn++ ions. In each Zn ion going into the solution, two electrons are left on the zind rod. As the concetration Zn++ ions in the solution increases, zinc rod becomes more and more negative and the H+ ions dilute through the walls of the porus pot into the CuSO solution.
Jain Educationa International
247
For Personal and Private Use Only
www.jainelibrary.org
