GIPHOTOSTOCK / SCIENCE PHOTO LIBRARY GIPHOTOSTOCK / SCIENCE PHOTO LIBRARY
Copper ion solutions. Left: 0.5M copper sulfate water solution - the blue colour due to a copper aquo complex formation ( (Cu(H2O)6)2+ ). Right: after excess ammonium hydroxide is added to the solution, tetraaminediaqua complex ( (Cu(NH3)4(H2O))2+ ) is formed and the solution colour changes to dark blue.
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