Сравнение скоростей диффузии (закон Грэма)

Сравнение скоростей диффузии газов HCl и NH₃

Gas Laws Intermediate (High School) 30 мин ~$10,00

Цель

Проверить закон Грэма о диффузии, сравнив скорости, с которыми HCl и NH₃ проходят через стеклянную трубку.

Предпосылки

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.

Предупреждения по безопасности

  • 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

Требуемые СИЗ

goggles gloves lab_coat

Материалы

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

Оборудование

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

Процедура

1

Clamp the glass tube horizontally on the retort stand.

3 мин
2

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

2 мин 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 мин Work quickly
4

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

10 мин
5

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

3 мин
6

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

5 мин

Ожидаемые результаты

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.

Уборка

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

Детали

Категория
Gas Laws
Сложность
Intermediate (High School)
Продолжительность
30 мин
Прим. стоимость
$10,00
Шаги
6
Материалы
3

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Frequently Asked Questions

What is the objective of Сравнение скоростей диффузии (закон Грэма)?
Проверить закон Грэма о диффузии, сравнив скорости, с которыми HCl и NH₃ проходят через стеклянную трубку.
How difficult is Сравнение скоростей диффузии (закон Грэма)?
This experiment is rated as Intermediate (High School). It takes approximately 30 minutes to complete.
What safety precautions are needed for Сравнение скоростей диффузии (закон Грэма)?
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 Сравнение скоростей диффузии (закон Грэма)?
The main materials required are: Concentrated hydrochloric acid, Concentrated ammonia solution, Cotton wool.
What results should I expect from Сравнение скоростей диффузии (закон Грэма)?
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.