Question
Sat March 22, 2014 By: Harini A

if in a galvanic cell anode is loss of electrons and cathode is gain of electrons,then how is anode -ve and cathode +ve

Expert Reply
Mon March 24, 2014
  • In both galvanic cell and electrolytic cell, reduction takes place at cathode and oxidation takes place at anode. But the sign conventions changes  for these electrodes.
  • Anode is a positively charged terminal where oxidation reaction takes place. Oxidation reactions involve the loss of electrons. As the reaction progresses, the oxidation terminal loses electrons to the electrolyte. Negative charge is moving away from the oxidation site. A positive current would move towards the oxidation site, against the flow of electrons. Since current flows to the anode, the oxidation site is the anode of the cell.
  • Cathode is a negatively charged terminal where reduction reaction takes place. Reduction reactions involve the gain of electrons. Electrons are needed to fuel the reaction and pull these electrons from the electrolyte. Since electrons are attracted to the reduction site and current flows opposite the flow of electrons, current flows away from the reduction site. Since current flows from the cathode to the anode, the reduction site is the cathode.
Thus, the anode of a galvanic cell is negatively charged, since the spontaneous oxidation at the anode is the source of the cell's electrons or negative charge. The cathode of a galvanic cell is its positive terminal.

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