Gujarat BoardEnglish MediumSTD 12 ScienceChemistryElectrochemistry3 Marks
Question
What is cell potential and emf? Explain representation of galvanic cell with examples?
✓
Answer
$\rightarrow $ "The potential difference between the two electrodes of a galvanic cell is called the cell potential and it is measured in volts."
$\rightarrow $ The cell potential is the difference between the electrode potentials $($reduction potentials$)$ of the cathode and anode. It is called the cell electromotive force $\text{(EMF)}$ of the cell when no current is drawn through the cell.
$ E _{\text {cell }}= E _{\text {right }}- E _{\text {left }} Or$
$E _{\text {cell }}= E _{\text {red(cathode) }}- E _{\text {red(anode) }}$ Cell Representation:
$\rightarrow $ We keep the anode on the left and the cathode on the right while representing the galvanic cell.
$\rightarrow $ A glavanic cell is generally represented by putting a vertical line between metal and electrolyte solution and putting a double vertical line between the two electrolytes connected by a salt bridge
Anode half cell $||$ cathode half cell
Example :
Cell reaction :
$Cu ( s )+2 Ag ^{+}( aq ) \rightarrow Cu ^{2+}( aq )+2 Ag ( s )$
Half$-$cell reaction :
Cathode $($reduction$) : 2 Ag ^{+}( aq )+2 e ^{-} \rightarrow 2 Ag ( s )$
Anode $($oxidation$) : Cu ( s ) \rightarrow Cu ^{2+}( aq )+2 e ^{-}$
$\rightarrow $ Silver electrode acts as a cathode and copper electrode acts as an anode. The cell can be represented as :
$Cu ( s )\left| Cu ^{2+}( aq ) \| Ag ^{+}( aq )\right| Ag ( s )$and we have $E _{\text {cell }}= E _{\text {right }}- E _{\text {left }}= E _{ Ag ^{+} \mid Ag }- E _{ Cu ^2 \mid Cu }$
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