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2.7.8Atoms, Elements and Compounds

Practical- Prepare Copper(II)Sulfate — Cambridge IGCSE Chemistry 0620 Revision Notes & Topical Questions

5 min read 4 parts Lesson 16 of 26 Unit quiz

📚 Cambridge IGCSE Chemistry 0620 Hub / Topical Revision
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Section 1 of 4Method

The method follows the insoluble base method for preparing a soluble salt.

1
Measure 50 cm³ of 1.0 mol/dm³ dilute sulfuric acid into a beaker and warm it gently using a Bunsen burner or water bath.
2
Add copper(II) oxide slowly to the hot acid, stirring with a glass rod until the oxide is in excess and some of it no longer dissolves.
3
Filter the mixture into an evaporating basin to remove the excess black copper(II) oxide.
4
Heat the filtrate gently to evaporate some water, then test for saturation by dipping a cold glass rod into the solution to see whether crystals form on it.
5
Leave the saturated solution in a warm place to crystallise, then decant the excess liquid and dry the crystals.

Section 2 of 4Apparatus and Safety

Correct apparatus and careful heating ensure a safe and accurate preparation.

Measuring cylinder
  • Measuring cylinder Used to measure 50 cm³ of dilute acid accurately before it is warmed in the beaker.
Filter funnel
  • Filter funnel Holds the filter paper so the excess copper(II) oxide is removed from the warm solution.
Water bath
  • Water bath Gives gentle, even heating, which avoids overheating and spitting of the solution.
Safety
  • Safety Dilute sulfuric acid is corrosive, so eye protection should be worn throughout the practical.

Section 3 of 4Expected Results

Expected Results
Crystals
  • Crystals Hydrated copper(II) sulfate forms bright blue, regularly shaped crystals.
Excess base
  • Excess base Adding oxide in excess means no acid remains to become concentrated during evaporation.
Overall equation
  • Overall equation CuO(s) + H₂SO₄(aq) → CuSO₄(aq) + H₂O(l).
Improving crystals
  • Improving crystals Leaving the filtrate to cool slowly gives larger crystals than rapid cooling.

Section 4 of 4Exam Checklist & Tips

2.7.8 – Key Points for the Exam

  • Saturated A solution that cannot dissolve more solute at that temperature.
  • Hydrated salt A salt that contains water of crystallisation as part of its crystal structure.
  • Decant To pour off the liquid from settled crystals.
  • Excess More reactant than needed, so that the other reactant is completely used up.

Common Mistakes

  • Evaporating the solution to dryness, which overheats the copper sulfate and may decompose it.
  • Adding too little copper(II) oxide, so unreacted acid is left in the solution.
  • Failing to filter out the excess base before evaporating, which contaminates the crystals.
  • Describing the crystals as green; hydrated copper(II) sulfate is bright blue.

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