Pile à Concentration

Génération d'une tension à partir de différences de concentration

Electrochemistry Advanced (University) 45 min ~$18,00

Objectif

Construire une pile à concentration en utilisant des demi-piles de cuivre à différentes concentrations et vérifier la prédiction de l'équation de Nernst pour le potentiel de pile.

Contexte

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.

Avertissements de sécurité

  • Copper sulfate is toxic
  • Wear gloves when handling solutions

EPI requis

goggles gloves lab_coat

Matériaux

  • 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

Équipement

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

Procédure

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

Résultats attendus

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.

Nettoyage

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

Détails

Catégorie
Electrochemistry
Difficulté
Advanced (University)
Durée
45 min
Coût estimé
$18,00
Étapes
7
Matériaux
3

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Frequently Asked Questions

What is the objective of Pile à Concentration?
Construire une pile à concentration en utilisant des demi-piles de cuivre à différentes concentrations et vérifier la prédiction de l'équation de Nernst pour le potentiel de pile.
How difficult is Pile à Concentration?
This experiment is rated as Advanced (University). It takes approximately 45 minutes to complete.
What safety precautions are needed for Pile à Concentration?
Key safety precautions include: Copper sulfate is toxic; Wear gloves when handling solutions.
What materials are needed for Pile à Concentration?
The main materials required are: Copper(II) sulfate (CuSO₄), Copper strips (2), Potassium nitrate salt bridge.
What results should I expect from Pile à Concentration?
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.