Question

Which of the following statement (s) is (are) not correct with reference to ferrous and ferric ions?
A. \[F{e^{3 + }}\] gives brown colour with potassium ferricyanide
B. \[F{e^{2 + }}\] gives blue ppt with potassium ferricyanide
C. \[F{e^{3 + }}\] gives red colour with potassium sulphocyanide
D. \[F{e^{2 + }}\] gives brown colour with potassium sulphocyanide

Answer 1

Hint: The atomic number of irons is 26 and hence its electronic configuration is \[1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^6}\] . Hence, the iron atom can achieve 2 oxidation states, viz. +2 and +3. The ion with +2 oxidation state is known as ferrous ion whereas the ion with +3 oxidation state is known as ferric ion

Complete Step-by-Step Answer:
Before we move forward with the solution of the given question, let us first understand some important basic concepts.
. Because of this variable oxidation state, iron has the capacity to form compounds with a number of chemical substituents.
Now, let us discuss all the options one by one.
 \[F{e^{3 + }}\] gives brown colour with potassium ferricyanide:
Potassium ferricyanide will react with \[F{e^{3 + }}\] to form a brown coloration of the compound. Also, this brown is because of the coloration of the compound, and no because of the formation of a precipitate.

 \[F{e^{2 + }}\] gives blue ppt with potassium ferricyanide
Potassium ferricyanide when reacted with \[F{e^{2 + }}\] forms a precipitate which is dark blue in colour. This precipitate is also referred to as Turnbull’s Blue, while it is still similar to Prussian Blue. The chemical reaction for the same can be given as:
 \[KFe[Fe{(CN)_6}] \rightleftharpoons {K^ + } + F{e_2}^ + + {[Fe{(CN)_6}]^{3 - }}\]

 \[F{e^{3 + }}\] gives red colour with potassium sulphocyanide:
Potassium sulphocyanide or potassium thiocyanate reacts with \[F{e^{3 + }}\] to form a compound which forms a compound that has a deep red colour. The chemical reaction for the same can be given as:
 \[K{[FeNCS]_2} \rightleftharpoons F{e^{3 + }} + NC{S^ - } + {K^ + }\]

 \[F{e^{2 + }}\] gives brown colour with potassium sulphocyanide:
Potassium sulphocyanide or potassium thiocyanide reacts with \[F{e^{2 + }}\] to form a compound which also forms a compound that has a deep red colour. The chemical formula for the same is given as:
  \[K{[FeNCS]^{2 + }} \rightleftharpoons F{e^{3 + }} + 2NC{S^ - } + {K^ + }\]

Hence, Option is the correct option

Note: Potassium ferrocyanide is the inorganic compound with formula \[{K_4}[Fe{(CN)_6}].3{H_2}O\] . It is the potassium salt of the coordination complex \[{[Fe{(CN)_6}]^{4 - }}\] . This salt forms lemon-yellow monoclinic crystals.