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An equilibrium involving copper(II) ions

Description

Students add ammonia to a solution of copper(II) sulfate, observe the colour changes taking place and then reverse the reaction using sulfuric acid.

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

Each student or working group will require:

Eye protection

Test-tubes, 3

Test-tube rack

Test-tube holder

Dropping pipettes, 2

Copper(II) sulfate solution, 1.0 M (HARMFUL), about 3 cm3 (Note 1)

Ammonia solution, 1.0 M, about 10 cm3

Dilute sulfuric acid, 1.0 M (IRRITANT), about 10 cm3

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

 




If this experiment is being carried out with pre-A-level students, the reactions occurring can simply be explained by reference to the addition of an alkali (containing hydroxide ions) being added to a solution of a copper compound, producing copper(II) hydroxide initially and later a complex compound of ammonia. The reversal of the process is easy to explain since sulfuric acid is capable of neutralising the alkaline ammonia and causing the reaction to reverse back to the start:



Page last updated February 2016

Students add ammonia to a solution of copper(II) sulfate, observe the colour changes taking place and then reverse the reaction using sulfuric acid.

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.