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Reacting copper(II) oxide with sulfuric acid

Description

In this experiment an insoluble metal oxide is reacted with a dilute acid to form a soluble salt. Copper(II) oxide, a black solid, and colourless dilute sulfuric acid react to produce copper(II) sulfate, giving a characteristic blue colour to the solution. From this solution, blue copper(II) sulfate pentahydrate crystals can be obtained.

Credits

:
This is an experiment from the Practical Chemistry project, developed by the Nuffield Foundation and the Royal Society of Chemistry.
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Apparatus Chemicals

Eye protection

Each working group will require:

Glass beaker (100 cm3)

Conical flask (100 cm3)

Spatula

Glass stirring rod

Filter funnel (Note 1)

Filter paper (Note 2)

Bunsen burner, tripod and gauze

Heat resistant mat

pH or litmus paper

Dilute sulfuric acid, 0.5 M (IRRITANT), 20 cm3

Copper(II) oxide (HARMFUL, DANGEROUS FOR THE ENVIRONMENT), about 1 g

Refer to Health & Safety and Technical notes section below for additional information.

 

 


Read our standard health & safety guidance

 


Stage 1
a
 Add 20 cm3 of the 0.5 M sulfuric acid to the 100 cm3 beaker. Heat carefully on the tripod with a gentle blue flame until nearly boiling.

SAFETY: Be very careful not to knock the tripod while the beaker is on it.

b When the acid is hot enough (just before it starts to boil), use a spatula to add small portions of copper(II) oxide to the beaker. Stir the mixture gently for up to half a minute after each addition.

SAFETY: When adding the solid to the beaker, take care to avoid knocking the beaker.

c When all the copper(II) oxide has been added, continue to heat gently for 1 to 2 minutes to ensure reaction is complete. Then turn out the Bunsen burner. It may be wise to check (using pH or litmus paper) that no acid remains. If the acid has not been hot enough, excess acid can co-exist with copper oxide. If someone should decide to attempt to evaporate the acid after filtering, the lab would fill with fumes.

d Allow the beaker to cool slightly while you set up Stage 2.

Stage 2
e
 Place the filter funnel in the neck of the conical flask.

f Fold the filter paper to fit the filter funnel, and put it in the funnel.

g Make sure the beaker is cool enough to hold at the top. The contents should still be hot.

h Gently swirl the contents to mix, and then pour into the filter paper in the funnel. Allow to filter through.

i A clear blue solution should collect in the flask. If the solution is not clear, and black powder remains in it, you will need to repeat the filtration.

Stage 3 (optional)
j Rinse the beaker, and pour the clear blue solution back into it. Label the beaker with your name(s). Leave the beaker in a warm place, where it won't be disturbed, for a week or so. This will enable most of the water to evaporate.

k Before all the water has evaporated, you should find some crystals forming on the bottom of the beaker. Filter the solution. Collect the crystals from the filter paper onto a paper towel.

 






 


In this experiment an insoluble metal oxide is reacted with a dilute acid to form a soluble salt. Copper(II) oxide, a black solid, and colourless dilute sulfuric acid react to produce copper(II) sulfate, giving a characteristic blue colour to the solution. From this solution, blue copper(II) sulfate pentahydrate crystals can be obtained.

ADDITIONAL INFORMATION

This is a resource from the Practical Chemistry project, developed by the Nuffield Foundation and the Royal Society of Chemistry. This collection of over 200 practical activities demonstrates a wide range of chemical concepts and processes. Each activity contains comprehensive information for teachers and technicians, including full technical notes and step-by-step procedures. Practical Chemistry activities accompany Practical Physics and Practical Biology .