Page 14 - Curriculum Visions Dynamic Book

Iron oxides
Iron oxide can occur in two forms, depending on how much oxygen is bound with the iron. Compounds of iron with a lower oxygen content are known as ferrous compounds, whereas the compounds
of iron with the higher oxygen content are known as ferric compounds.
Ferric compounds
Ferric compounds
(also known as iron III compounds) have a yellow, red or brown colour.
The red–brown gelatinous precipitate in the bottom of the tube shown here is ferric hydroxide (iron III hydroxide).
Ferrous compounds
The colour of the iron compound is related to the amount of oxygen it contains. Ferrous compounds (also known as iron II compounds) have a green, grey or blue colour.
The dirty-looking green gelatinous precipitate in the bottom of the tube on the right is a ferrous hydroxide (iron II hydroxide).
 How it was made
The gelatinous red–brown precipitate of ferric hydroxide has been prepared by adding colourless sodium hydroxide solution to a yellow, ferric chloride (iron III choride) solution. An excess of ferric chloride remains, leaving the solution yellow.
EQUATION: Producing ferric hydroxide (iron III hydroxide)
Sodium hydroxide + iron III chloride ➪ iron III hydroxide + sodium chloride 3NaOHaq) + FeCl3(aq) ➪ Fe(OH)3(s) + 3NaCl(aq)
14