扩散速率比较（格雷厄姆定律）

比较HCl和NH₃气体的扩散速率

Gas Laws Intermediate (High School) 30 分钟 ~$10.00

目标

通过比较HCl和NH₃气体在玻璃管中的传播速率来验证格雷厄姆扩散定律。

背景

Graham's law states that the rate of diffusion of a gas is inversely proportional to the square root of its molar mass. When HCl (36.5 g/mol) and NH₃ (17 g/mol) diffuse toward each other in a tube, they form a white ring of NH₄Cl where they meet. The ring forms closer to the HCl end because NH₃ diffuses faster.

安全警告

  • Concentrated HCl fumes are corrosive and irritating
  • Concentrated ammonia fumes are irritating
  • Perform this experiment in a fume hood or well-ventilated area
  • Do not inhale either gas directly

所需PPE

goggles gloves lab_coat

材料

  • Concentrated hydrochloric acid (5 mL)
    For HCl fumes
  • Concentrated ammonia solution (5 mL)
    For NH₃ fumes
  • Cotton wool (2 pieces)
    For soaking

设备

Glass tube (1 m long, 2 cm diameter) Rubber stoppers (2) Ruler Retort stand and clamps Stopwatch

步骤

1

Clamp the glass tube horizontally on the retort stand.

3 分钟
2

In a fume hood, soak one cotton ball in concentrated HCl and another in concentrated ammonia.

2 分钟 Fume hood — both gases are irritating
3

Simultaneously insert the HCl cotton ball into one end and the NH₃ cotton ball into the other end. Stopper both ends.

2 分钟 Work quickly
4

Start the timer. Watch for a white ring of NH₄Cl to form where the two gases meet.

10 分钟
5

When the white ring appears, stop the timer. Measure the distance from each end to the ring.

3 分钟
6

Calculate the ratio of distances: d(NH₃)/d(HCl) should equal √(M(HCl)/M(NH₃)) = √(36.5/17) = 1.46.

5 分钟

预期结果

The white NH₄Cl ring should form approximately 60% of the way from the HCl end (40% from the NH₃ end), since NH₃ diffuses 1.46 times faster than HCl. The ratio d(NH₃)/d(HCl) should be approximately 1.4-1.5.

清理

Remove cotton balls and dispose in fume hood. Rinse the glass tube with water. Ventilate the area.

详情

类别
Gas Laws
难度
Intermediate (High School)
时长
30 分钟
预估费用
$10.00
步骤数
6
材料
3

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Frequently Asked Questions

What is the objective of 扩散速率比较（格雷厄姆定律）?
通过比较HCl和NH₃气体在玻璃管中的传播速率来验证格雷厄姆扩散定律。
How difficult is 扩散速率比较（格雷厄姆定律）?
This experiment is rated as Intermediate (High School). It takes approximately 30 minutes to complete.
What safety precautions are needed for 扩散速率比较（格雷厄姆定律）?
Key safety precautions include: Concentrated HCl fumes are corrosive and irritating; Concentrated ammonia fumes are irritating; Perform this experiment in a fume hood or well-ventilated area.
What materials are needed for 扩散速率比较（格雷厄姆定律）?
The main materials required are: Concentrated hydrochloric acid, Concentrated ammonia solution, Cotton wool.
What results should I expect from 扩散速率比较（格雷厄姆定律）?
The white NH₄Cl ring should form approximately 60% of the way from the HCl end (40% from the NH₃ end), since NH₃ diffuses 1.46 times faster than HCl. The ratio d(NH₃)/d(HCl) should be approximately 1.4-1.5.