CBSE Class 12 Chemistry 2025: question 18

Hints

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Step-by-step solution

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1. (a) In acidic medium permanganate is reduced to $\mathrm{M}{\mathrm{n}}^{2+}$ and iodide is oxidised to iodine:
   $2\mathrm{Mn}{\mathrm{O}}_4^{-}(\mathrm{aq})+10{\mathrm{I}}^{-}(\mathrm{aq})+16{\mathrm{H}}^{+}(\mathrm{aq})\to 2\mathrm{M}{\mathrm{n}}^{2+}(\mathrm{aq})+5{\mathrm{I}}_2(\mathrm{s})+8{\mathrm{H}}_2\mathrm{O}(\mathrm{l})$

   1 mark

2. (b) In acidic medium dichromate is reduced to $\mathrm{C}{\mathrm{r}}^{3+}$ and $\mathrm{F}{\mathrm{e}}^{2+}$ is oxidised to $\mathrm{F}{\mathrm{e}}^{3+}$:
   $\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_7^{2-}(\mathrm{aq})+6\mathrm{F}{\mathrm{e}}^{2+}(\mathrm{aq})+14{\mathrm{H}}^{+}(\mathrm{aq})\to 2\mathrm{C}{\mathrm{r}}^{3+}(\mathrm{aq})+6\mathrm{F}{\mathrm{e}}^{3+}(\mathrm{aq})+7{\mathrm{H}}_2\mathrm{O}(\mathrm{l})$

   1 mark

Answer: (a) → 2Mn²⁺ + 5I₂ + 8H₂O; (b) → 2Cr³⁺ + 6Fe³⁺ + 7H₂O

Revise the chapter

• Chapter: The d- and f-Block Elements (notes, formulas, where marks are lost and every past question)