An electrochemical cell is a system that converts chemical energy into electrical energy through spontaneous redox reactions. These cells are commonly used in batteries and power sources.
An electrochemical cell consists of two half-cells, each containing an electrode immersed in an electrolyte. The two half-cells are connected by a salt bridge, which allows the flow of ions to maintain electrical neutrality.
Oxidation occurs at the anode, while reduction occurs at the cathode. Electrons flow from the anode to the cathode through the external circuit.
A common example is the Daniell cell, which consists of a zinc electrode in zinc sulfate solution and a copper electrode in copper sulfate solution.
\[\text{Zn (s)} \rightarrow \text{Zn}^{2+} (aq) + 2e^-\]
\[\text{Cu}^{2+} (aq) + 2e^- \rightarrow \text{Cu (s)}\]
The overall cell reaction is:
\[\text{Zn (s)} + \text{Cu}^{2+} (aq) \rightarrow \text{Zn}^{2+} (aq) + \text{Cu (s)}\]
The potential difference (emf) of the cell depends on the nature of the electrodes and the concentrations of the electrolyte solutions.
\[E_{\text{cell}} = E_{\text{cathode}} - E_{\text{anode}}\]
A potential difference is observed on the voltmeter. The anode gradually dissolves into the solution, while the cathode gains mass due to deposition of metal.
The salt bridge allows ions to move between the two half-cells, preventing the buildup of charge that would otherwise stop the flow of electrons.
Electrical energy is generated from a spontaneous redox reaction. The flow of electrons through the external circuit and ions through the salt bridge sustains the operation of the cell.
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