Hydrogen peroxide oxidises $\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-}$ to $\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}$ in acidic medium but reduces $\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}$ to $\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-}$ in alkaline medium. The other products formed are, respectively :

(D) $\mathrm{H}_{2} \mathrm{O}$ and $\left(\mathrm{H}_{2} \mathrm{O}+\mathrm{O}_{2}\right)$

(A) $\mathrm{H}_{2} \mathrm{O}$ and $\left(\mathrm{H}_{2} \mathrm{O}+\mathrm{OH}^{-}\right)$

(B) $\left(\mathrm{H}_{2} \mathrm{O}+\mathrm{O}_{2}\right)$ and $\mathrm{H}_{2} \mathrm{O}$

(C) $\left(\mathrm{H}_{2} \mathrm{O}+\mathrm{O}_{2}\right)$ and $\left(\mathrm{H}_{2} \mathrm{O}+\mathrm{OH}^{-}\right)$

JEE Main · 2018 · 08 Apr 2018 · Offline · Hydrogen

Hydrogen peroxide oxidises

[Fe (CN)_{6}]^{4 -}

[Fe (CN)_{6}]^{3 -}

in acidic medium but reduces

[Fe (CN)_{6}]^{3 -}

[Fe (CN)_{6}]^{4 -}

in alkaline medium. The other products formed are, respectively :

Answer: (D)

In acid

H X_{2} O X_{2}

acts as an oxidant, taking electrons and being reduced to water, so as it oxidises

[Fe (CN) X_{6}] X^{4 -}

[Fe (CN) X_{6}] X^{3 -}

the accompanying product is

H X_{2} O

. In alkali

H X_{2} O X_{2}

instead acts as a reductant, giving up electrons and being oxidised to oxygen, so as it reduces

[Fe (CN) X_{6}] X^{3 -}

back to

[Fe (CN) X_{6}] X^{4 -}

the products are

H X_{2} O

and

O X_{2}

. The other products are therefore

H X_{2} O

in the acidic case and

H X_{2} O

together with

O X_{2}

in the alkaline case.

JEE Main · 2018 · 08 Apr 2018 · Offline · Single correct option