Iodometric Titration of Bleach

Determining the concentration of sodium hypochlorite in household bleach

Titrations Advanced (University) 50 min ~$15.00

Objective

Determine the sodium hypochlorite (NaOCl) concentration in commercial bleach using iodometric titration with sodium thiosulfate.

Background

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.

Safety Warnings

  • 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

Required PPE

goggles gloves lab_coat

Materials

  • 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)

Equipment

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

Procedure

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

Expected Results

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.

Cleanup

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

Details

Category
Titrations
Difficulty
Advanced (University)
Duration
50 min
Est. Cost
$15.00
Steps
8
Materials
6

More Experiments

Acid-Base Titration with Methyl Orange 40 min Acid-Base Titration with Phenolphthalein 45 min Back Titration of Antacid Tablets 60 min Conductometric Titration 50 min Double Indicator Titration of Carbonate-Bicarbonate Mixture 55 min EDTA Complexometric Titration of Water Hardness 45 min pH Titration Curve 50 min Precipitation Titration (Mohr Method) 45 min Redox Titration with Potassium Permanganate 50 min Vitamin C Titration with Iodine 40 min

Frequently Asked Questions

What is the objective of Iodometric Titration of Bleach?
Determine the sodium hypochlorite (NaOCl) concentration in commercial bleach using iodometric titration with sodium thiosulfate.
How difficult is Iodometric Titration of Bleach?
This experiment is rated as Advanced (University). It takes approximately 50 minutes to complete.
What safety precautions are needed for Iodometric Titration of Bleach?
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 Iodometric Titration of Bleach?
The main materials required are: Household bleach, Potassium iodide (KI), Sodium thiosulfate (Na₂S₂O₃), Starch indicator, Acetic acid (CH₃COOH).
What results should I expect from Iodometric Titration of Bleach?
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.