酚酞酸碱滴定

用标准碱溶液测定酸的浓度

Titrations Intermediate (High School) 45 分钟 ~$15.00

目标

以酚酞为指示剂，用标准化氢氧化钠溶液滴定未知浓度的盐酸溶液，测定其浓度。

背景

This classic acid-base titration demonstrates stoichiometric neutralization. HCl reacts with NaOH in a 1:1 molar ratio. Phenolphthalein turns pink above pH 8.2, providing a clear endpoint. Accurate burette technique and multiple trials are essential for reliable results.

安全警告

  • NaOH is corrosive — avoid skin and eye contact
  • HCl is corrosive — handle with care
  • Wear safety goggles throughout
  • Wash any spills immediately with water

所需PPE

goggles gloves lab_coat

材料

  • Hydrochloric acid (HCl) (100 mL)
    Unknown concentration
  • Sodium hydroxide (NaOH) (100 mL)
    0.1M standardized
  • Phenolphthalein indicator (5 mL)
    1% in ethanol
  • Distilled water (500 mL)
    For rinsing

设备

50 mL burette Burette stand and clamp 250 mL Erlenmeyer flask 25 mL pipette Pipette filler White tile Wash bottle

步骤

1

Rinse the burette with a small amount of NaOH solution, then fill it to the 0 mL mark. Record the exact starting volume.

5 分钟 Handle NaOH carefully
2

Using the pipette and filler, transfer exactly 25.0 mL of the unknown HCl solution into the Erlenmeyer flask.

3 分钟
3

Add 2-3 drops of phenolphthalein indicator to the flask. The solution should remain colorless (acidic).

1 分钟
4

Place the flask on the white tile under the burette. Begin adding NaOH slowly while swirling the flask continuously.

5 分钟
5

As the endpoint approaches (pink color lingers longer), add NaOH drop by drop until a permanent pale pink color persists for 30 seconds.

5 分钟
6

Record the final burette reading. Calculate the volume of NaOH used.

2 分钟
7

Repeat the titration at least two more times for concordant results (within 0.10 mL).

15 分钟
8

Calculate the concentration of HCl using: C(HCl) = C(NaOH) x V(NaOH) / V(HCl).

5 分钟

预期结果

The endpoint should show a clear transition from colorless to a persistent pale pink. Concordant titre values (within 0.10 mL) indicate good technique. The calculated concentration should match the expected value within experimental error.

清理

Drain the burette and rinse with distilled water. Neutralize waste solutions before disposal. Rinse all glassware thoroughly.

详情

类别
Titrations
难度
Intermediate (High School)
时长
45 分钟
预估费用
$15.00
步骤数
8
材料
4

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Frequently Asked Questions

What is the objective of 酚酞酸碱滴定?
以酚酞为指示剂，用标准化氢氧化钠溶液滴定未知浓度的盐酸溶液，测定其浓度。
How difficult is 酚酞酸碱滴定?
This experiment is rated as Intermediate (High School). It takes approximately 45 minutes to complete.
What safety precautions are needed for 酚酞酸碱滴定?
Key safety precautions include: NaOH is corrosive — avoid skin and eye contact; HCl is corrosive — handle with care; Wear safety goggles throughout.
What materials are needed for 酚酞酸碱滴定?
The main materials required are: Hydrochloric acid (HCl), Sodium hydroxide (NaOH), Phenolphthalein indicator, Distilled water.
What results should I expect from 酚酞酸碱滴定?
The endpoint should show a clear transition from colorless to a persistent pale pink. Concordant titre values (within 0.10 mL) indicate good technique. The calculated concentration should match the expected value within experimental error.