50.2 MB (50.0 MB compressed)
5119 x 3425 pixels
43.4 x 29.0 cm ⏐ 17.1 x 11.4 in (300dpi)
MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
Iron chlorides. Iron (II) chloride and iron (III) chloride contain iron (Fe) ions with different combining powers, as indicated by the oxidation state included in the names of the compounds. Both are soluble in water, but the Fe +3 ion forms a yellow colour in solution, whereas the colour formed by the Fe +2 ion is a pale green. This is due to the formation of complex hydrated ions in water, respectively the hexaaqua ion (6 water molecules) and the tetraaqua ion (4 water molecules). Acid equilibria and ionic effects lead to other ions and the colours observed, which get stronger with concentration.
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