Subject: Inorganic Chemistry · Chapter: D Block · Topic: D Block – General · Exam: JAM 2005-2022 · Marks: 2 · Difficulty: Easy
6(a) Consider the reaction(I) $\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}+\mathrm{H}_{2} \mathrm{O}_{2} \xrightarrow{\mathrm{A}} \underset{\text { Unstable }}{\mathrm{CrO}\left(\mathrm{O}_{2}\right)_{2}} \xrightarrow{\text { room temperature }} \mathrm{Cr}^{3+}$ (II) $\mathrm{Cr}^{3+}+\mathrm{H}_{2} \mathrm{O}_{2} \xrightarrow{\mathrm{B}} \mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}$ (i) Identify A and B. (ii) What is the role of $\mathrm{H}_{2} \mathrm{O}_{2}$ in (I) and how does A favour the formation of $\mathrm{Cr}^{3+}$ ? (iii) What is the role of $\mathrm{H}_{2} \mathrm{O}_{2}$ in (II) and how does B favour the formation $\mathrm{CrO}_{4}{ }^{2-}$ ?
(b)With the help of equations, illustrate the role of a cis-1, 2-diol in the titration of boric acid with sodium hydroxide.