Titrage Iodométrique de l'Eau de Javel

Détermination de la concentration en hypochlorite de sodium dans l'eau de javel domestique

Titrations Advanced (University) 50 min ~$15,00

Objectif

Déterminer la concentration en hypochlorite de sodium (NaOCl) dans l'eau de javel commerciale par titrage iodométrique au thiosulfate de sodium.

Contexte

In iodometric titrations, the analyte (hypochlorite) oxidizes iodide ions to iodine, which is then titrated with sodium thiosulfate. The endpoint is detected using starch indicator. This indirect method is widely used for determining the concentration of oxidizing agents.

Avertissements de sécurité

  • Bleach is an irritant and oxidizer
  • Do not mix bleach with acid in large quantities — produces chlorine gas
  • Work in a well-ventilated area or fume hood
  • Wear safety goggles and gloves

EPI requis

goggles gloves lab_coat

Matériaux

  • Household bleach (50 mL)
    Dilute 1:10 before use
  • Potassium iodide (KI) (5 g)
    Excess
  • Sodium thiosulfate (Na₂S₂O₃) (100 mL)
    0.1M standardized
  • Starch indicator (10 mL)
    1% solution
  • Acetic acid (CH₃COOH) (20 mL)
    2M
  • Distilled water (300 mL)

Équipement

50 mL burette Burette stand and clamp 250 mL Erlenmeyer flask 25 mL pipette 25 mL volumetric flask

Procédure

1

Prepare a 1:10 dilution of the bleach with distilled water in the volumetric flask.

3 min Bleach is irritating
2

Pipette 25.0 mL of the diluted bleach into the Erlenmeyer flask.

2 min
3

Add approximately 2 g of potassium iodide. The solution will turn brown/yellow as iodine is liberated.

2 min
4

Add 10 mL of 2M acetic acid to acidify the solution.

1 min Work in ventilated area
5

Fill the burette with 0.1M sodium thiosulfate. Begin titrating the brown iodine solution.

5 min
6

When the solution becomes pale yellow, add 1 mL of starch indicator. The solution turns dark blue.

2 min
7

Continue titrating drop by drop until the blue color disappears and the solution becomes colorless.

5 min
8

Record the volume. Repeat for concordant results. Calculate the NaOCl concentration accounting for the dilution.

15 min

Résultats attendus

Household bleach typically contains 3-8% NaOCl. The endpoint should show a sharp transition from blue to colorless. Multiple concordant results should agree within 0.10 mL.

Nettoyage

Neutralize iodine waste with sodium thiosulfate before disposal. Rinse all glassware. Ensure proper ventilation during cleanup.

Détails

Catégorie
Titrations
Difficulté
Advanced (University)
Durée
50 min
Coût estimé
$15,00
Étapes
8
Matériaux
6

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Frequently Asked Questions

What is the objective of Titrage Iodométrique de l'Eau de Javel?
Déterminer la concentration en hypochlorite de sodium (NaOCl) dans l'eau de javel commerciale par titrage iodométrique au thiosulfate de sodium.
How difficult is Titrage Iodométrique de l'Eau de Javel?
This experiment is rated as Advanced (University). It takes approximately 50 minutes to complete.
What safety precautions are needed for Titrage Iodométrique de l'Eau de Javel?
Key safety precautions include: Bleach is an irritant and oxidizer; Do not mix bleach with acid in large quantities — produces chlorine gas; Work in a well-ventilated area or fume hood.
What materials are needed for Titrage Iodométrique de l'Eau de Javel?
The main materials required are: Household bleach, Potassium iodide (KI), Sodium thiosulfate (Na₂S₂O₃), Starch indicator, Acetic acid (CH₃COOH).
What results should I expect from Titrage Iodométrique de l'Eau de Javel?
Household bleach typically contains 3-8% NaOCl. The endpoint should show a sharp transition from blue to colorless. Multiple concordant results should agree within 0.10 mL.