1. Experiment Snapshot
| Feature | Details |
|---|
| Apparatus | Conical flask, delivery tube, bung, gas jar/test tube, water trough if collecting over water. |
| Chemicals/Reagents | Zinc or magnesium, dilute hydrochloric acid or sulfuric acid. |
| Main observation | Effervescence occurs; hydrogen gives a squeaky pop with a lighted splint. |
| Main measurement | Gas collection and positive gas test. |
2. Aim
To prepare hydrogen gas and test it using a lighted splint.
3. Quick Theory
Reactive metals react with dilute acids to produce a salt and hydrogen gas.
Zn + 2HCl → ZnCl₂ + H₂
Examiner Tip: Hydrogen gives a squeaky pop with a lighted splint.
4. Apparatus, Chemicals and Safety
| Category | Details |
|---|
| Apparatus | Conical flask, delivery tube, bung, gas jar/test tube, water trough if collecting over water. |
| Chemicals | Zinc or magnesium, dilute hydrochloric acid or sulfuric acid. |
Safety: Wear goggles. Acid is irritant/corrosive. Hydrogen is flammable, so test only small samples away from bulk gas.
5. Labelled Experiment Diagram
Preparation and Testing of Hydrogen — Premium Practical Setup
6. Procedure
- Place zinc granules or magnesium in a conical flask.
- Add dilute acid carefully.
- Fit bung and delivery tube quickly.
- Allow first bubbles to escape because they may contain air.
- Collect hydrogen in a test tube or gas jar.
- Bring a lighted splint to the mouth of the test tube.
- Listen for a squeaky pop.
- Record observations.
Examiner Tip: Use a lighted splint for hydrogen; glowing splint is for oxygen.
7. Observations and Results
| Stage / Test | Observation | Conclusion |
|---|
| Reaction flask | Effervescence | Gas produced |
| Gas test | Squeaky pop | Hydrogen present |
| First gas | May be mixed with air | Discard first bubbles |
Conclusion: Hydrogen is prepared by reacting a suitable metal with dilute acid and identified by the squeaky pop test.
8. Calculations / Key Chemical Reasoning
The metal displaces hydrogen from the acid because it is more reactive than hydrogen.
metal + acid → salt + hydrogen
Worked Example:
Zinc + hydrochloric acid forms zinc chloride and hydrogen gas.
9. Sources of Error and Improvements
| Source of Error | Effect | Improvement |
|---|
| Gas leaks | Less hydrogen collected | Check airtight setup |
| First gas contains air | Impure/unsafe mixture | Discard first bubbles |
| Acid too concentrated | Reaction too vigorous | Use dilute acid |
| Using too much metal | Excessive gas | Use small amount |
| Wrong splint test | Misidentification | Use lighted splint |
10. Student Common Mistakes
- Using glowing splint.
- Calling gas oxygen.
- Not discarding first gas.
- Holding flame near reaction flask.
- Forgetting hydrogen is flammable.
11. Examiner Tips
Tip: Hydrogen gives squeaky pop.
Tip: Use dilute acid.
Tip: First gas may contain air.
Tip: Metal must be more reactive than hydrogen.
12. Examiner Traps
Trap: Hydrogen test uses lighted splint, not glowing splint.
Trap: Hydrogen is flammable; use small sample.
Trap: Not all metals react safely with acid.
13. 🎮 Interactive Simulator
Hydrogen Gas Test
Choose conditions and test gas.
Observation Window
Gas tube
Choose a condition and run the simulation.
Lab Score: 0/0
14. Past Paper Style Questions
- State the aim of this experiment. [2 marks]
- Name the main apparatus or reagent used. [2 marks]
- Describe the key observation expected. [2 marks]
- Give one safety precaution. [1 mark]
- Give one source of error and one improvement. [2 marks]
- Explain the chemistry behind the result. [3 marks]
15. Mark Scheme Answers
Q1. To prepare and test hydrogen gas [2].
Q2. Metal, dilute acid, delivery tube, gas jar [2].
Q3. Fizzing and squeaky pop with lighted splint [2].
Q4. Keep flame away from reaction flask; goggles [1].
Q5. Gas leak; check airtight setup [2].
Q6. Metal reacts with acid to form salt and hydrogen [3].
16. Quick Revision Card
| Key Point | Memory Hook |
|---|
| Gas | Hydrogen |
| Test | squeaky pop |
| Reagents | metal + acid |
| Safety | flammable |
| First bubbles | discard |
17. Mastery Checklist
- I can prepare hydrogen.
- I can state test.
- I can write word equation.
- I can describe safety.
- I can identify errors.