Question

Which of the following can be oxidised by acidified $K_{2}C{r}_2{O}_7$?

• A. Nitrate ions
• B. Sulphite ions
• C. Ferric ions
• D. Borate ions

Answer 1

Answer: (B)

Sulphite ions

$C{r}_2{O}_7^{2-}+3\stackrel{+4}{S}O{{}_3}^{2-}+8H^{+}⟶2C{r}^{3+}+3\stackrel{+6}{S}O{{}_4}^{2-}+4H_{2}O$

$\therefore K_{2}C{r}_2{O}_7$ can oxidize sulphite ions $\left(SO{{}_3}^{2-}\right)$ to $SO{{}_4}^{2-}$.

Nitrate ion, ferric ion, and borate ions are already in their highest oxidation state thus they cannot be further oxidized.