Uploaded July 2015 | Updated September 2026, 2 weeks ago
An aqueous solution of copper(II) sulfate is blue in colour owing to the formation of hexaaquacopper(II) ions, which have an octahedral crystal field.
As sodium chloride is added to the solution, the colour changes from blue to green due to the formation of yellow tetrachlorocuprate(II) complexes, which have a tetrahedral crystal field. The green colour is due to the mixing of the yellow chloro-complex with the blue aqua-complex.
An aqueous solution of copper(II) sulfate is blue in colour owing to the formation of hexaaquacopper(II) ions, which have an octahedral crystal field.
As sodium chloride is added to the solution, the colour changes from blue to green due to the formation of yellow tetrachlorocuprate(II) complexes, which have a tetrahedral crystal field. The green colour is due to the mixing of the yellow chloro-complex with the blue aqua-complex.
