Question

The formula of Prussian blue is :
a.) $N{a_4}[Fe{(CN)_6}]$
b.) $Fe{(CN)_2}$
c.) $Fe{(CNS)_3}$
d.) $F{e_4}{[Fe{(CN)_6}]_3}$

Answer 1

The Prussian blue is the dark blue pigment. It is chemically identical to Turnbull’s blue. It is formed by oxidation of ferrous ferrocyanide salts. It is also called Berlin blue or Ferric ferrocyanide or Ferric hexacyanoferrate and Parisian blue etc.

Complete step by step answer :
These types of questions are easy to do if we remember the formula and can fetch us marks in second because we need not do anything other than a tick on the right answer. But if we don’t know then a single guess can even deduct our marks. So, let us see the formula of Prussian blue. It is chemically identical to Turnbull’s blue. The formula is - $F{e_4}{[Fe{(CN)_6}]_3}$.

So, the option d.) is the correct answer.

Additional information :
Prussian blue is insoluble in water. So, it is prepared as colloidal dispersion. It is used in paints and blueprints. Medically, it is an antidote for certain kinds of heavy metal poisoning.

Note: There are many other compounds that have such common names. These can also be remembered. Some of them are in the following table.

Compound Name	Chemical Name	Formula
Blue Vitriol	Copper Sulphate	$CuS{O_4} \cdot 5{H_2}O$
Green Vitriol	Ferrous Sulphate	$FeS{O_4} \cdot 7{H_2}O$
Epsom	Magnesium Sulphate	$MgS{O_4} \cdot 7{H_2}O$
Plaster of Paris	Calcium Sulphate (anhydrous)	$CaS{O_4} \cdot \frac{1}{2}{H_2}O$
Gypsum	Calcium Sulphate	$CaS{O_4} \cdot 2{H_2}O$
Washing soda	Sodium Carbonate	$NaC{O_3} \cdot 10{H_2}O$
Chalk	Calcium Carbonate	$CaC{O_3}$
Common salt or Rock salt	Sodium Chloride	NaCl
Quick lime	Calcium oxide	CaO
Slaked lime or Milk of lime	Calcium hydroxide	$Ca{(OH)_2}$