Titrage Conductimétrique

Suivi d'un titrage par la conductivité électrique

Titrations Advanced (University) 50 min ~$20,00

Objectif

Effectuer un titrage acide-base en utilisant des mesures de conductivité plutôt qu'un indicateur, et déterminer le point d'équivalence à partir d'un graphique conductivité-volume.

Contexte

In a conductometric titration, electrical conductivity of the solution is measured as the titrant is added. Since different ions have different molar conductivities (H+ and OH- are exceptionally mobile), the conductivity changes non-linearly during titration. The endpoint is found where two straight-line segments of the conductivity curve intersect.

Avertissements de sécurité

  • HCl and NaOH are corrosive
  • Wear safety goggles and gloves
  • Keep the conductivity probe away from the magnetic stirrer bar

EPI requis

goggles gloves lab_coat

Matériaux

  • Hydrochloric acid (HCl) (100 mL)
    0.1M
  • Sodium hydroxide (NaOH) (100 mL)
    0.1M
  • Distilled water (200 mL)

Équipement

50 mL burette Burette stand and clamp 250 mL beaker Conductivity meter with probe Magnetic stirrer 25 mL pipette Graph paper

Procédure

1

Pipette 25.0 mL of 0.1M HCl into the beaker. Add 50 mL of distilled water to increase volume for the probe.

3 min Handle HCl carefully
2

Place the beaker on the magnetic stirrer. Insert the conductivity probe and the stir bar.

2 min
3

Record the initial conductivity reading. Fill the burette with 0.1M NaOH.

3 min
4

Add 1.0 mL of NaOH from the burette. Stir for 30 seconds, then record the conductivity and cumulative volume.

2 min
5

Repeat step 4, adding 1.0 mL increments, recording conductivity after each addition. Continue until well past the expected endpoint.

25 min
6

Plot conductivity (y-axis) versus volume of NaOH added (x-axis). Identify the two linear regions.

8 min
7

Draw best-fit lines for the two regions and find their intersection. This is the endpoint.

5 min

Résultats attendus

Conductivity initially decreases as highly mobile H+ ions are replaced by less mobile Na+ ions. After the endpoint, conductivity increases as excess OH- ions accumulate. The V-shaped graph clearly shows the equivalence point.

Nettoyage

Remove and rinse the conductivity probe carefully. Neutralize waste solutions before disposal. Rinse all glassware.

Détails

Catégorie
Titrations
Difficulté
Advanced (University)
Durée
50 min
Coût estimé
$20,00
Étapes
7
Matériaux
3

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Frequently Asked Questions

What is the objective of Titrage Conductimétrique?
Effectuer un titrage acide-base en utilisant des mesures de conductivité plutôt qu'un indicateur, et déterminer le point d'équivalence à partir d'un graphique conductivité-volume.
How difficult is Titrage Conductimétrique?
This experiment is rated as Advanced (University). It takes approximately 50 minutes to complete.
What safety precautions are needed for Titrage Conductimétrique?
Key safety precautions include: HCl and NaOH are corrosive; Wear safety goggles and gloves; Keep the conductivity probe away from the magnetic stirrer bar.
What materials are needed for Titrage Conductimétrique?
The main materials required are: Hydrochloric acid (HCl), Sodium hydroxide (NaOH), Distilled water.
What results should I expect from Titrage Conductimétrique?
Conductivity initially decreases as highly mobile H+ ions are replaced by less mobile Na+ ions. After the endpoint, conductivity increases as excess OH- ions accumulate. The V-shaped graph clearly shows the equivalence point.