ABOUT Zinc Carbon Cell (20點!!)

because in zinc-carbon cell, the electrolyte is ammonium chloride. as the cell reacts ammonium ion becomes ammonia and hydrogen, and the hydrogen is formed on the surface of the positive electrode, therefore electric-conductivity of the cell decreases. however in better zinc-carbon cells it has manganese(IV) oxide which would react with hydrogen gas formed at positive electrode, in order to maintain electric-conductivity. However if the rate of discharge of the cell is too great, rate of reaction of manganese(IV) oxide with hydrogen is not fast enough so the cell would eventually fail to operate but after certain period of time, hydrogen gas are reacted and the cell would work again~