Question

Which of the following compounds after mixing can produce blue colouration?
I. $K_4\left[Fe\right(CN{)}_6]$ and $FeC{l}_3$ solution
II. $N{H}_{4}OH$ and $CuS{O}_4$ solution
III. Adding anhydrous $CuS{O}_4$ to water
IV. $N{H}_{4}OH+NiS{O}_4$ solution

• A. I, II, III
• B. II, III
• C. I, III
• D. I, II, III, IV

Answer 1

The correct option is D I, II, III, IV

$2C{u}^{2+}+S{O}_4^{2-}+2N{H}_3+2H_{2}O\to Cu(OH{)}_2.CuS{O}_4\downarrow +2N{H}_4^{+}$

$Cu(OH{)}_2.CuS{O}_4\downarrow +8N{H}_3\to 2[Cu(N{H}_3{)}_4{]}^{2+}+S{O}_4^{2-}+2O{H}^{-}$

$4F{e}^{3+}+3\left[Fe\right(CN{)}_6{]}^{4-}\to F{e}_4\left[Fe\right(CN{)}_6{]}_3\downarrow$

$Ni(OH{)}_2\downarrow +6N{H}_3\to [Ni(N{H}_3{)}_6{]}^{2+}+2O{H}^{-}$

$Ni(OH{)}_2\downarrow +6N{H}_4^{+}+4O{H}^{-}\to [Ni(N{H}_3{)}_6{]}^{2+}+6H_{2}O$

All of them produce blue coloured compounds.