Page 15 - Curriculum Visions Dynamic Book

Drops of sodium hydroxide being released from a dropper.
gelatinous: a term meaning made with water. Because a gelatinous precipitate is mostly water, it is of
a similar density to water and will float or lie suspended in the liquid.
Also...
Many other iron compounds have striking colours. They have been known and used since ancient times.
Ochre
Ochre is the name given to yellow–red colours produced by iron compounds. Ochre is a powder
made by crushing many iron-rich ores. Limonite and haematite (see page 13) produce yellow and
red colouring, respectively. If either of these ores is roasted, the colours will darken to red–brown.
This is called burnt ochre. The powder is used in paints as the colouring agent or pigment.
It is mixed with a liquid before being applied.
Prussian blue
Prussian blue (so named because it was developed in Prussia during the 18th
century) is obtained by reacting iron oxide with potassium ferrocyanide.
It is used as a “whitener” in washing powders, being a
light blue dye that gives the optical illusion of whiteness
to clothes. In more concentrated form it acts
as a blue pigment in paints and enamels.
Gelatinous, drop-shaped, precipitated solid forms as
the drop of sodium hydroxide falls into the solution containing ferrous sulphate.
 How it was made
The green, gelatinous precipitate of ferrous hydroxide (iron II hydroxide) was prepared
by adding colourless sodium hydroxide solution
to ferrous sulphate (iron II sulphate) solution.
EQUATION: Producing ferrous hydroxide (iron II hydroxide)
Sodium hydroxide + iron II chloride ➪ iron II hydroxide + sodium chloride 2NaOH(aq) + FeCl2(aq) ➪ Fe(OH)2(s) + 2NaCl(aq)
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