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Daniell cell

It's a Zn|Zn²⁺||Cu²⁺|Cu battery. When both the circuit and the salt bridge are connected, electrons and ions move. Distinguish between open-circuit voltage and current flow calculated by concentration.

    C19 · Daniell cellReady
    It's a Zn|Zn²⁺||Cu²⁺|Cu battery. When both the circuit and the salt bridge are connected, electrons and ions move. Distinguish between open-circuit voltage and current flow calculated by concentration. You can also experiment with the numbers and controls below.

    Chemistry · Electrochemistry / Principles and Exploration

    Daniell cell — principles and investigation

    The Daniel cell using zinc and copper is a device that converts oxidation and reduction reactions into electrical energy. Connect electron transfer and cell reaction by changing the ion concentration, external circuit, and salt bridge conditions. Electron movement in a metal conductor and ion movement in a salt bridge are two different types of charge transfer.

    How does it work?

    Electron flow requires charge balancing through closed external circuits and salt bridges. In a salt bridge, ions, not electrons, move.

    Key relationship

    E = 1.10 − (0.0592/2) log₁₀([Zn²⁺]/[Cu²⁺])

    Try this investigation

    1. It's a Zn|Zn²⁺||Cu²⁺|Cu battery. When both the circuit and the salt bridge are connected, electrons and ions move. Distinguish between open-circuit voltage and current flow calculated by concentration.
    2. Record the voltage under the conditions of both concentrations of 1 mol/L and Cu²⁺ of only 0.01 mol/L.
    3. Under standard conditions, compare whether the flow becomes 0 by separating only the salt bridge or opening only the circuit.

    Interpreting your results

    What is the movement of electrons and salt bridge ions in the external conductor?

    Zn is oxidized and gives up electrons, and Cu²⁺ is reduced. A salt bridge maintains charge balance on both sides of the solution by moving ions.

    Assumptions and limitations

    As long as 25 °C and E°=1.10 V, it is the Nernst model. Concentration is used instead of activity level. The voltmeter displays the calculated open-circuit voltage. When separating the salt bridge, the actual terminal voltage is not predicted. The current is a relative indicator of connection, E/1.10, not the actual current in A. Internal resistance, polarization, concentration consumption, liquid-to-liquid potential, and instantaneous transient current are excluded. When disconnected, the continuous current is immediately treated as 0.