Skip to content
Grade 10 Advanced About 20 min Version 1 Awaiting review Premium

Making blue copper sulfate crystals

A salt is made when an acid reacts with a base. Copper oxide is a base that does not dissolve in water, but it reacts with sulfuric acid: copper oxide + sulfuric acid → copper sulfate + water. Copper sulfate is a blue salt that dissolves in the water made. Adding the copper oxide until no more reacts makes sure all the acid is used up. The leftover copper oxide is filtered off, and the blue solution is evaporated so that crystals of the salt form.

What you will learn

  • Prepare a soluble salt from an insoluble base and an acid.
  • Explain why excess copper oxide is added and then filtered off.
  • Describe crystallization of a salt from its solution.

Before you start

  • Know about filtration and evaporation. Try "Getting salt back from a salt and sand mixture" first.

Materials

  • Dilute sulfuric acid
  • Copper(II) oxide powder

Equipment

  • Beaker on a hot plate
  • Conical flask with funnel and filter paper
  • Evaporating dish
  • Stirring rod

Procedure

  1. Warm the dilute sulfuric acid in Beaker A to about 50 °C.
  2. Add black copper oxide powder and stir. Keep adding until some stays undissolved.
  3. Filter the mixture into Flask B to remove the excess copper oxide.
  4. Pour the blue filtrate into Dish C, heat it and evaporate the water so crystals form.

How this simulation is simplified

  • The reaction is shown happening as soon as the mixture is warm and stirred.
  • Evaporation is shown until dry. In real crystallization the solution is only partly evaporated and then left to cool slowly.