Conc Acid Oxidizer
Watch carbon and copper get oxidized
What this lesson covers
Why it matters
Concentrated sulphuric acid is so greedy for oxygen that it rips it from other elements, turning copper into a blue solution and releasing choking fumes.
The idea in plain words
Analyze the redox process: Copper loses electrons to become Cu²⁺ (blue), while H₂SO₄ gains electrons to form SO₂.
Predict first
Why does concentrated sulphuric acid react with copper, while dilute acid does not?
Concentrated H₂SO₄ decomposes to release nascent oxygen [O], which oxidizes copper. Dilute acid lacks this oxidizing power.
- Concentrated acid is simply more acidic (more H⁺ ions)
- Concentrated acid acts as a strong oxidizing agent, releasing nascent oxygen — correct
- Heat is required to melt the copper
What you do
Run all three reactions. Observe the gases evolved and the color changes in the solution.
Check yourself
What is the primary observation when copper reacts with hot concentrated sulphuric acid?
Cu + 2H₂SO₄ → CuSO₄ (blue) + SO₂ (suffocating smell) + 2H₂O.
C + 2H₂SO₄ → CO₂ + 2SO₂ + 2H₂O releases two gases that BOTH turn limewater milky. How do you tell them apart?
Limewater alone cannot separate them — CO₂ gives CaCO₃ and SO₂ gives CaSO₃, both milky. The suffocating smell (or SO₂ decolourising acidified KMnO₄) identifies SO₂.
Why does sulphur react with concentrated H₂SO₄ to produce only SO₂?
S + 2H₂SO₄ → 3SO₂ + 2H₂O. The acid acts as an oxidizer, not a proton donor.
- Effervescence of colourless, odourless gas
- Formation of a blue solution and a gas with a suffocating smell — correct
- No reaction occurs
- SO₂ has a suffocating burning-sulphur smell; CO₂ is odourless — correct
- Only CO₂ turns limewater milky, so no further test is needed
- CO₂ is the one with the suffocating smell
- Sulphur is oxidized by the nascent oxygen from the acid — correct
- Sulphur displaces hydrogen from the acid
- Sulphur decomposes the acid into water and oxygen only