Question

${\text{F}}{{\text{e}}^{3 + }}\left( {{\text{aq}}{\text{.}}} \right)$ reacts with aqueous ${\text{KSCN}}$ to give a deep red solution due to the formation of $\left[ {{\text{Fe}}{{\left( {{\text{SCN}}} \right)}^{{\text{2 + }}}}} \right]$. If true enter 1, else enter 0.

Answer 1

The ${\text{F}}{{\text{e}}^{3 + }}\left( {{\text{aq}}{\text{.}}} \right)$ ions react with aqueous ${\text{KSCN}}$ and lead to the formation of the complex $\left[ {{\text{Fe}}{{\left( {{\text{SCN}}} \right)}^{{\text{2 + }}}}} \right]$. The ligands ${\text{SC}}{{\text{N}}^ - }$ have unpaired electrons.

Complete step by step answer:
${\text{F}}{{\text{e}}^{3 + }}\left( {{\text{aq}}{\text{.}}} \right)$ reacts with aqueous ${\text{KSCN}}$ to give a deep red solution due to the formation of thiocyanatoiron ion, $\left[ {{\text{Fe}}{{\left( {{\text{SCN}}} \right)}^{{\text{2 + }}}}} \right]$. The colour of ${\text{F}}{{\text{e}}^{3 + }}\left( {{\text{aq}}{\text{.}}} \right)$ ion is yellow and ${\text{SC}}{{\text{N}}^ - }$ ion is colourless.
The reaction is carried out in a slightly acidic medium in the presence of nitric acid which makes the solution slightly acidic.
The ligands, thiocyanate ions, ${\text{SC}}{{\text{N}}^ - }$ have unpaired electrons. The thiocyanate ion is the conjugate base of thiocyanic acid.
The unpaired electrons lead to the deep red solution.
Thus, the statement ‘${\text{F}}{{\text{e}}^{3 + }}\left( {{\text{aq}}{\text{.}}} \right)$ reacts with aqueous ${\text{KSCN}}$ to give a deep red solution due to the formation of $\left[ {{\text{Fe}}{{\left( {{\text{SCN}}} \right)}^{{\text{2 + }}}}} \right]$’ is true.

Additional Information:
Thiocyanate is soluble in water and is very acidic in nature. Thiocyanate ion is a pseudohalide anion. It is obtained by the deprotonation of thiol group of thiocyanic acid.
Thiocyanate ion is found in the smoke of cigarettes and plants like cabbage, broccoli, cauliflower, sprouts, etc. Thiocyanate ion is highly toxic and causes muscle weakness, confusion and coma if consumed in higher concentrations. In an adequate amount, thiocyanate is used for the treatment of hypertensive emergencies.
The saliva also contains thiocyanate which does not allow microbial growth in the oral cavity.

Note:
The deep red colour of the $\left[ {{\text{Fe}}{{\left( {{\text{SCN}}} \right)}^{{\text{2 + }}}}} \right]$ complex makes it easy to be detected by spectrophotometry. In dilute solutions, the colour changes to orange.