The Excess Solid Method
Making a Soluble Salt from an Acid + Insoluble Solid (Metal, Base, or Carbonate)
The Coffee Brewing Analogy
In the Kitchen ☕
You scoop excess coffee grounds into hot water. The water becomes super-strong. You pour it through a filter — muddy grounds stay behind. Pure, smooth coffee drips through.
In the Lab ⚗️
You add excess CuO (black powder) to warm H₂SO₄. The acid is fully neutralised. You filter — excess CuO stays in the paper. Pure CuSO₄(aq) drips through.
🔬 Interactive Lab Bench
Click a stage to animate it
Warm Beaker
⚗️ H₂SO₄(aq) + CuO(s) → CuSO₄(aq) + H₂O(l)
Black CuO powder piles up at the bottom — this is the EXCESS ensuring all acid reacts!
Filter Funnel + Paper
Evaporating Basin
HAZARD WARNING
Dilute H₂SO₄ is corrosive. Wear safety goggles and gloves. Hot liquids can splash — heat gently. Copper(II) sulfate is harmful if ingested.
❓ The "Why" Checkpoints
Tap each question — these are examiner favourites!
🔀 Step Sorter Challenge
Drag the steps into the correct order, then check your answer.
🔭 Apparatus Identifier
Hover over each apparatus to reveal its role.
Filter Funnel + Paper
Stage 2Evaporating Basin
Stage 3🧪 Examiner's Trap — Don't Lose Marks!
"The excess solid ensures the acid doesn't run out."
Wrong framing — the acid is the reagent we want to fully react.
"The excess solid ensures ALL the acid is neutralised so none contaminates the product."
This earns marks — it explains the purpose precisely.
"Heat until dry to get the crystals."
Boiling dry destroys the crystal structure!
"Evaporate until crystallisation point, then allow to cool slowly to form crystals."
Correct — never boil to dryness.
📋 Method Summary
- 1
Warm: Warm dilute sulfuric acid in a beaker
- 2
Add Excess: Add excess CuO (black powder) with stirring — until no more dissolves and solid remains at the bottom
- 3
Filter: Filter the hot mixture using a filter funnel and paper — CuO (residue) stays in the paper; blue CuSO₄(aq) (filtrate) drips through
- 4
Evaporate: Heat the filtrate in an evaporating basin until ~half the water has boiled off
- 5
Cool: Remove from heat. Allow to cool slowly — blue CuSO₄·5H₂O crystals form
H₂SO₄(aq) + CuO(s) → CuSO₄(aq) + H₂O(l)
Sign In to Keep Going
You've reached the end of the free preview. Sign in — and upgrade to Plus or Pro — to keep going with Chemistry.
Full Access
Unlock all 320 lessons