Lab Prep: Zinc & Acid
The standard method for collecting hydrogen gas.
What this lesson covers
Why it matters
Zinc granules vanish into dilute sulphuric acid, releasing a colourless gas that gives a sharp 'pop' with a burning splinter.
The idea in plain words
Map the atoms: Zinc displaces Hydrogen from the acid molecule.
Predict first
Why is this method preferred for preparing pure hydrogen in the lab?
Zinc and dilute acid react at a steady, moderate rate, allowing safe collection of the gas — reducing the risk of a violent reaction without being too sluggish.
- The reaction is violent and explosive
- It produces hydrogen at a steady, controllable rate — correct
- Sulfuric acid is cheaper than water
- Zinc is the only metal that reacts with acid
What you do
Add zinc to the acid. Observe the effervescence and test the gas with a burning splinter.
Check yourself
What is the chemical equation for this reaction?
Zinc displaces hydrogen from dilute sulfuric acid to form zinc sulfate and hydrogen gas.
How do you confirm the gas is hydrogen?
Hydrogen burns rapidly with oxygen in the air, creating a small explosion heard as a pop.
Why is dilute sulfuric acid used instead of nitric acid?
Nitric acid oxidizes the hydrogen produced to water, releasing nitrogen oxides instead.
- Zn + H₂SO₄ → ZnSO₄ + H₂ — correct
- Zn + H₂SO₄ → ZnS + H₂O + SO₂
- Zn + 2H₂SO₄ → Zn(HSO₄)₂ + H₂
- Zn + H₂SO₄ → ZnO + H₂ + SO₃
- It turns limewater milky
- A burning splinter produces a 'pop' sound — correct
- It relights a glowing splinter
- It turns blue litmus red
- Nitric acid is a strong oxidizing agent and does not typically release hydrogen with metals — correct
- Nitric acid is too expensive
- Sulfuric acid reacts faster
- Nitric acid is a weak acid and cannot displace hydrogen from metals