Smelting: Carbon vs Hydrogen

Why it matters

Black copper oxide turns into shiny red metal when hydrogen gas passes over it. The tube sweats with water droplets as the oxygen is stripped away.

The idea in plain words

Observe the swap: Hydrogen takes oxygen from copper(II) oxide. Identify the product that forms on the tube walls.

Predict first

Why can hydrogen reduce copper oxide, but not zinc oxide?

In the activity series, metals below hydrogen (like copper) can be reduced by it. Zinc is above hydrogen, so hydrogen cannot displace zinc from its oxide.

• Hydrogen is a gas and zinc oxide is a solid
• Copper is less reactive than hydrogen, so hydrogen can take its oxygen — correct
• Zinc oxide is too hard for hydrogen to penetrate
• Hydrogen only reacts with black powders

What you do

Run all three reactions. Note which ones require heat and what the final metal looks like.

Check yourself

Which observation confirms the reduction of CuO by H₂?

The reaction CuO + H₂ → Cu + H₂O produces reddish-brown copper metal and water vapor.

Why is carbon used to reduce lead oxide (PbO) instead of hydrogen?

While hydrogen can reduce some oxides, carbon is the standard industrial reducing agent for metals like lead because it is effective and economical. The equation is 2PbO + C → 2Pb + CO₂.

What gas is produced when zinc oxide is reduced by carbon?

The specific reaction for zinc oxide reduction is ZnO + C → Zn + CO. Unlike lead oxide, this reaction produces carbon monoxide.

• Formation of reddish-brown copper — correct
• Release of carbon dioxide gas
• The black powder turns white
• A loud explosion occurs
• Carbon is cheaper and more readily available for large-scale smelting — correct
• Hydrogen cannot reduce any metal oxides
• Lead is more reactive than carbon
• Hydrogen reacts too slowly with lead oxide
• Carbon monoxide (CO) — correct
• Carbon dioxide (CO₂)
• Oxygen (O₂)
• Hydrogen (H₂)