Iron nitrate is colorless or lavender monoclinic crystal,
True Fe3+ ions and hexahydrate Fe3+ ions are lavender.
However, due to the usual pH conditions, hydrated Fe3+ ions are easily hydrolyzed.
Partially hydrolyzed products such as Fe(OH)2+ and other hydroxylates and oxyhydroxides, OH- and O2- as ligands, their coordination field effect is very strong.
The 3d energy level of Fe3+ is changed to yellow and yellowish brown, which also makes the solution yellow.
In Fe(NO3)3 crystal, Fe3+ is composed of NO3- as a ligand
Without H2O or OH- as a ligand, Fe3+ will not hydrolyze.
Moreover, the coordination field effect of NO3- is weak and has no effect on the 3d energy level of Fe3+.
Therefore, Fe3+ exhibits its original color in Fe(NO3)3 crystal, namely lavender, Of course, its dilute solution is pale yellow.
If it is a concentrated solution, add concentrated HNO3 to inhibit its hydrolysis.
Due to NO3- participation, the color will approach lavender color.
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