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A cell with copper and zinc

In a galvanic cell, reduction happens at the cathode and oxidation at the anode. The metal with the lowest standard reduction potential becomes the anode, because it most easily gives away electrons. The cell voltage is the cathode potential minus the anode potential. The numbers below are the standard potentials from the theory: copper +0.34 V and zinc -0.76 V. Since zinc has the lower number, zinc is oxidised and the copper ions are reduced. A positive cell voltage means the reaction is spontaneous under standard conditions.

E^\circ = E^\circ_{\mathrm{cathode}} - E^\circ_{\mathrm{anode}}

standard cell voltage

Symbols

$\mathrm{Cu}^{2+}/\mathrm{Cu}$	+0.34	V
$\mathrm{Zn}^{2+}/\mathrm{Zn}$	-0.76	V

Example

Copper is the cathode and zinc is the anode.

$E^\circ = 0.34 - (-0.76) = 1.10$ V.

The electrons go in the wire from the anode to the cathode. The ions in the salt bridge keep the solutions neutral.

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Part of Chemistry 2: Electrochemistry.