Hydrogen Gas Collection

Generating and collecting hydrogen from zinc and acid

Gas Laws Intermediate (High School) 35 min ~$10.00

Objective

Generate hydrogen gas from the reaction of zinc with hydrochloric acid and collect it by water displacement.

Background

When zinc metal reacts with hydrochloric acid, hydrogen gas is produced: Zn + 2HCl → ZnCl₂ + H₂. The gas can be collected by water displacement in an inverted graduated cylinder, allowing volume measurement and mole calculations.

Safety Warnings

  • Hydrogen gas is extremely flammable — NO open flames nearby
  • HCl is corrosive
  • Work in a well-ventilated area
  • Do not seal the system completely — pressure buildup risk

Required PPE

goggles gloves lab_coat

Materials

  • Zinc granules (5 g)
  • Hydrochloric acid (HCl) (50 mL)
    2M
  • Distilled water (500 mL)

Equipment

Erlenmeyer flask (250 mL) Rubber stopper with delivery tube Pneumatic trough or large bowl Graduated cylinder (100 mL) Rubber tubing

Procedure

1

Fill the pneumatic trough with water. Fill the graduated cylinder with water, invert it, and place it in the trough.

5 min
2

Place 5 g zinc granules in the Erlenmeyer flask.

2 min
3

Add 50 mL of 2M HCl to the flask. Quickly insert the rubber stopper with delivery tube.

2 min HCl is corrosive
4

Direct the delivery tube under the inverted graduated cylinder. Collect the hydrogen gas by water displacement.

10 min No flames — hydrogen is flammable
5

When the reaction slows, record the volume of gas collected. Note temperature and atmospheric pressure.

3 min
6

Optionally, perform the squeaky pop test: bring a lit splint near a small collection of H₂.

3 min Very small amount only
7

Calculate moles of H₂ using ideal gas law and compare with moles predicted from zinc mass.

5 min

Expected Results

5 g Zn = 0.076 mol should produce 0.076 mol H₂ = ~1.9 L at STP. The collected volume should be close to this when corrected for temperature and water vapor pressure.

Cleanup

Neutralize remaining acid with sodium bicarbonate. Dispose of zinc chloride solution down the drain. Rinse all equipment.

Details

Category
Gas Laws
Difficulty
Intermediate (High School)
Duration
35 min
Est. Cost
$10.00
Steps
7
Materials
3

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Frequently Asked Questions

What is the objective of Hydrogen Gas Collection?
Generate hydrogen gas from the reaction of zinc with hydrochloric acid and collect it by water displacement.
How difficult is Hydrogen Gas Collection?
This experiment is rated as Intermediate (High School). It takes approximately 35 minutes to complete.
What safety precautions are needed for Hydrogen Gas Collection?
Key safety precautions include: Hydrogen gas is extremely flammable — NO open flames nearby; HCl is corrosive; Work in a well-ventilated area.
What materials are needed for Hydrogen Gas Collection?
The main materials required are: Zinc granules, Hydrochloric acid (HCl), Distilled water.
What results should I expect from Hydrogen Gas Collection?
5 g Zn = 0.076 mol should produce 0.076 mol H₂ = ~1.9 L at STP. The collected volume should be close to this when corrected for temperature and water vapor pressure.