EMF of an electrochemical cell template

Zinc in zinc sulfate and copper in copper(II) sulfate in two beakers, joined by a salt bridge, with a high-resistance voltmeter across the metal strips. A-level / AP / IB (CBSE class 12).

What the template shows

• Measure the voltage of a Zn | Zn²⁺ || Cu²⁺ | Cu cell with a salt bridge
• Zinc: negative electrode
• Zn → Zn²⁺ + 2e⁻. Clean both strips with emery paper
• 1.0 mol dm⁻³ ZnSO₄
• Copper in 1.0 mol dm⁻³ CuSO₄
• Positive electrode: Cu²⁺ + 2e⁻ → Cu
• Salt bridge
• Filter paper soaked in saturated KNO₃ (or KCl in agar): ions move to balance the charge without the solutions mixing
• High-resistance voltmeter
• Draws almost no current, so it reads the EMF: about +1.10 V at 298 K. Red lead to Cu (+), black to Zn (−)
• Reaction setup

Drawn with 22 shapes – every one editable in MolDraw.

Sources

• Atkins, de Paula & Keeler, Atkins' Physical Chemistry, 11th ed., OUP 2018 Textbook
• Housecroft & Sharpe, Inorganic Chemistry, 5th ed., Pearson 2018 Textbook