漂白剂碘量滴定

测定家用漂白剂中次氯酸钠的浓度

Titrations Advanced (University) 50 分钟 ~$15.00

目标

用硫代硫酸钠碘量滴定法测定商业漂白剂中次氯酸钠（NaOCl）的浓度。

背景

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.

安全警告

  • 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

所需PPE

goggles gloves lab_coat

材料

  • 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)

设备

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

步骤

1

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

3 分钟 Bleach is irritating
2

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

2 分钟
3

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

2 分钟
4

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

1 分钟 Work in ventilated area
5

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

5 分钟
6

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

2 分钟
7

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

5 分钟
8

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

15 分钟

预期结果

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.

清理

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

详情

类别
Titrations
难度
Advanced (University)
时长
50 分钟
预估费用
$15.00
步骤数
8
材料
6

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Frequently Asked Questions

What is the objective of 漂白剂碘量滴定?
用硫代硫酸钠碘量滴定法测定商业漂白剂中次氯酸钠（NaOCl）的浓度。
How difficult is 漂白剂碘量滴定?
This experiment is rated as Advanced (University). It takes approximately 50 minutes to complete.
What safety precautions are needed for 漂白剂碘量滴定?
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 漂白剂碘量滴定?
The main materials required are: Household bleach, Potassium iodide (KI), Sodium thiosulfate (Na₂S₂O₃), Starch indicator, Acetic acid (CH₃COOH).
What results should I expect from 漂白剂碘量滴定?
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.