Which of the following statements(s) is (are) correct with reference to the ferrous and ferric ions?

Question

Which of the following statements(s) is (are) correct with reference to the ferrous and ferric ions?\

Professor PC Thomas Classes · Answer

(b, c) : $\mathrm{Fe}^{2+}$ ions give blue ppt. with $\mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}ight]$. The blue ppt. appears due to the formation of Turnbull's blue; $\mathrm{KFe}\left[\mathrm{Fe}(\mathrm{CN})_{6}ight]$.\ $\mathrm{Fe}^{2+}+\mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}ight] \longrightarrow$ $$ \begin{aligned} & \mathrm{KFe}\left[\mathrm{Fe}(\mathrm{CN})_{6}ight]+2 \mathrm{~K}^{+} \ & 	ext {Potassium ferro- } \ & \quad 	ext { ferricyanide } \ & 	ext { (Turnbull's blue) } \end{aligned} $$ The red colouration that appears in case of $\mathrm{Fe}^{3+}$ ions on reaction with potassium thiocyanate (KCNS) is due to the formation of $\left[\mathrm{Fe}(\mathrm{CNS})_{3}ight]$.\ $\mathrm{Fe}^{3+}+3 \mathrm{KCNS} \longrightarrow \underset{\substack{	ext { Ferric thiocyanate } \ 	ext { (red) }}}{\left[\mathrm{Fe}(\mathrm{CNS})_{3}ight]}+3 \mathrm{~K}^{+}$\