In electrolytic cell, normally the metal in anode is oxidised to give out electrons and cathode takes electrons to from metal.
In zinc production, the anode is lead ( Pb) and the cathode is aluminium (Al) and the eletrolyte is zinc sulfate ( ZnSO4)
My question is why in the anode, the water is oxidised but not the lead metal???
2007-09-17 23:57:13 · 2 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
This process is called "zinc electrowinning". The lead metal will oxidized! and coat the lead with PbO2. Anode corrosion occurs and replacement anodes are inserted on a scheduled basis.
Zinc is more difficult to electrwinnin than most other metals, like copper, because zinc is far above hydrogen in the electrochemical series. So, the evolution of hydrogen from an acidic zinc sulfate solution is energetically favored over zinc deposition. As it happens, hydrogen evolution on a zinc surface is a very slow process (it occurs at a high overpotential) and hence zinc can be electrodeposited from acid solutions.
2007-09-21 17:33:04 · answer #1 · answered by Metallic stuff 7 · 0⤊ 0⤋
its the polarity
plus takes from minus
2007-09-20 19:15:41 · answer #2 · answered by M 5 · 0⤊ 0⤋