Concentration Cell

Generating voltage from concentration differences

Electrochemistry Advanced (University) 45 min ~$18.00

Objective

Construct a concentration cell using copper half-cells at different concentrations and verify the Nernst equation prediction for cell potential.

Background

A concentration cell generates voltage from the difference in concentration between two otherwise identical half-cells. According to the Nernst equation, the EMF depends on the logarithm of the concentration ratio. This experiment demonstrates that even without different metals, a potential difference arises from entropy-driven mixing.

Safety Warnings

  • Copper sulfate is toxic
  • Wear gloves when handling solutions

Required PPE

goggles gloves lab_coat

Materials

  • Copper(II) sulfate (CuSO₄) (200 mL total)
    Prepare 0.01M and 1M solutions
  • Copper strips (2) (2 pieces)
    Identical, sanded clean
  • Potassium nitrate salt bridge (1)
    Saturated KNO₃ in agar

Equipment

Two 250 mL beakers High-impedance voltmeter Wires with alligator clips Sandpaper Volumetric flasks

Procedure

1

Prepare two CuSO₄ solutions: 100 mL of 1.0M and 100 mL of 0.01M.

5 min Wear gloves
2

Sand both copper strips until shiny and rinse with distilled water.

3 min
3

Pour the dilute (0.01M) CuSO₄ into one beaker and the concentrated (1.0M) into the other.

2 min
4

Place one copper strip in each beaker. Connect with the salt bridge.

3 min
5

Connect the voltmeter. The dilute side is the anode (negative terminal). Measure the EMF.

5 min
6

Calculate the predicted EMF using the Nernst equation: E = (RT/nF) ln(C_high/C_low) = (0.0257/2) ln(100) = 0.059 V at 25°C.

5 min
7

Compare measured and theoretical values. Discuss sources of deviation.

5 min

Expected Results

The cell should produce approximately 0.05-0.06 V. The Nernst equation predicts E = (0.02569 V / 2) x ln(1.0/0.01) = 0.059 V at 25°C. Measured values may be slightly lower due to junction potentials.

Cleanup

Dispose of copper sulfate waste in designated containers. Rinse and store copper strips. Clean salt bridge.

Details

Category
Electrochemistry
Difficulty
Advanced (University)
Duration
45 min
Est. Cost
$18.00
Steps
7
Materials
3

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Frequently Asked Questions

What is the objective of Concentration Cell?
Construct a concentration cell using copper half-cells at different concentrations and verify the Nernst equation prediction for cell potential.
How difficult is Concentration Cell?
This experiment is rated as Advanced (University). It takes approximately 45 minutes to complete.
What safety precautions are needed for Concentration Cell?
Key safety precautions include: Copper sulfate is toxic; Wear gloves when handling solutions.
What materials are needed for Concentration Cell?
The main materials required are: Copper(II) sulfate (CuSO₄), Copper strips (2), Potassium nitrate salt bridge.
What results should I expect from Concentration Cell?
The cell should produce approximately 0.05-0.06 V. The Nernst equation predicts E = (0.02569 V / 2) x ln(1.0/0.01) = 0.059 V at 25°C. Measured values may be slightly lower due to junction potentials.