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 :
$\ce{Cu (s) + 2Ag^{+}(aq) \rightarrow Cu^{2+}(aq) + 2Ag(s)}$
Half$-$cell reaction :
Cathode (reduction) : $\ce{2Ag^{+}(aq) + 2e ^{-} \rightarrow 2Ag(s)}$
Anode (oxidation) : $\ce{Cu(s) \rightarrow Cu^{2+}( aq ) + 2e^{-}}$
$\rightarrow$ 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 $E _{\text {cell }}= E _{\text {right }}- E _{\text {left }}= E _{ Ag ^{+} \mid Ag }- E _{ Cu ^2 \mid Cu }$
$\rightarrow$ 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 :
$\ce{Cu (s) + 2Ag^{+}(aq) \rightarrow Cu^{2+}(aq) + 2Ag(s)}$
Half$-$cell reaction :
Cathode (reduction) : $\ce{2Ag^{+}(aq) + 2e ^{-} \rightarrow 2Ag(s)}$
Anode (oxidation) : $\ce{Cu(s) \rightarrow Cu^{2+}( aq ) + 2e^{-}}$
$\rightarrow$ 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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