JEE Challenger
More from The d- and f-Block Elements
ChemHardAdv 2007 • Paper 2

Matching Inorganic Chemical Reactions with Product Characteristics

Match the reactions in Column I with nature of the reactions/type of the products in Column II. Indicate your answer by darkening the appropriate bubbles of the 4×44 \times 4 matrix given in the ORS.

Column IColumn II(A) O2−→O2+O22−(p) redox reaction(B) CrO42−+H+→(q) one of the products has trigonal planar structure(C) MnO4−+NO2−+H+→(r) dimeric bridged tetrahedral metal ion(D) NO3−+H2SO4+Fe2+→(s) disproportionation\begin{array}{ll} \textbf{Column I} & \textbf{Column II} \\[6pt] \text{(A) } \text{O}_2^- \rightarrow \text{O}_2 + \text{O}_2^{2-} & \text{(p) redox reaction} \\[6pt] \text{(B) } \text{CrO}_4^{2-} + \text{H}^+ \rightarrow & \text{(q) one of the products has trigonal planar structure} \\[6pt] \text{(C) } \text{MnO}_4^- + \text{NO}_2^- + \text{H}^+ \rightarrow & \text{(r) dimeric bridged tetrahedral metal ion} \\[6pt] \text{(D) } \text{NO}_3^- + \text{H}_2\text{SO}_4 + \text{Fe}^{2+} \rightarrow & \text{(s) disproportionation} \end{array}

Options

A

(A)→(p,s),  (B)→(r),  (C)→(p,q),  (D)→(p)(\text{A}) \rightarrow (\text{p}, \text{s}),\; (\text{B}) \rightarrow (\text{r}),\; (\text{C}) \rightarrow (\text{p}, \text{q}),\; (\text{D}) \rightarrow (\text{p})

Correct
B

(A)→(p),  (B)→(r,s),  (C)→(q),  (D)→(p,q)(\text{A}) \rightarrow (\text{p}),\; (\text{B}) \rightarrow (\text{r}, \text{s}),\; (\text{C}) \rightarrow (\text{q}),\; (\text{D}) \rightarrow (\text{p}, \text{q})

C

(A)→(s),  (B)→(q),  (C)→(p,r),  (D)→(p)(\text{A}) \rightarrow (\text{s}),\; (\text{B}) \rightarrow (\text{q}),\; (\text{C}) \rightarrow (\text{p}, \text{r}),\; (\text{D}) \rightarrow (\text{p})

D

(A)→(p,s),  (B)→(q),  (C)→(p),  (D)→(r)(\text{A}) \rightarrow (\text{p}, \text{s}),\; (\text{B}) \rightarrow (\text{q}),\; (\text{C}) \rightarrow (\text{p}),\; (\text{D}) \rightarrow (\text{r})

Topics & Concepts

The d- and f-Block ElementsRedox ReactionsDichromatePermanganateDisproportionation

Step-by-Step Solution

Step-by-step Evaluation:

  1. (A) O2−→O2+O22−\text{O}_2^- \rightarrow \text{O}_2 + \text{O}_2^{2-}:
  • Superoxide ion (oxidation state −1/2-1/2) undergoes self-oxidation-reduction to dioxygen O2\text{O}_2 (state 00) and peroxide ion O22−\text{O}_2^{2-} (state −1-1).
  • This is both a redox reaction (pp) and a disproportionation (ss).
  • Matching: (A)→(p,s)(\text{A}) \rightarrow (\text{p}, \text{s}).
  1. (B) CrO42−+H+→\text{CrO}_4^{2-} + \text{H}^+ \rightarrow:
  • In acidic medium, yellow chromate condenses to orange dichromate:
    2CrO42−+2H+→Cr2O72−+H2O2\text{CrO}_4^{2-} + 2\text{H}^+ \rightarrow \text{Cr}_2\text{O}_7^{2-} + \text{H}_2\text{O}
  • Dichromate is a dimeric bridged tetrahedral metal ion consisting of two CrO4\text{CrO}_4 tetrahedra sharing a common oxygen vertex (Cr−O−Cr\text{Cr}-\text{O}-\text{Cr}). Oxidation state of Cr remains +6+6 (non-redox).
  • Matching: (B)→(r)(\text{B}) \rightarrow (\text{r}).
  1. (C) MnO4−+NO2−+H+→\text{MnO}_4^- + \text{NO}_2^- + \text{H}^+ \rightarrow:
  • Permanganate oxidizes nitrite to nitrate in acidic solution:
    2MnO4−+5NO2−+6H+→2Mn2++5NO3−+3H2O2\text{MnO}_4^- + 5\text{NO}_2^- + 6\text{H}^+ \rightarrow 2\text{Mn}^{2+} + 5\text{NO}_3^- + 3\text{H}_2\text{O}
  • This is a redox reaction (pp). Moreover, nitrate ion (NO3−\text{NO}_3^-) possesses sp2sp^2 hybridization with a trigonal planar structure (qq).
  • Matching: (C)→(p,q)(\text{C}) \rightarrow (\text{p}, \text{q}).
  1. (D) NO3−+H2SO4+Fe2+→\text{NO}_3^- + \text{H}_2\text{SO}_4 + \text{Fe}^{2+} \rightarrow:
  • This is the brown-ring test reaction: nitrate oxidizes Fe2+\text{Fe}^{2+} to Fe3+\text{Fe}^{3+} while being reduced to NO\text{NO}, which coordinates with excess Fe2+\text{Fe}^{2+} to form [Fe(H2O)5(NO)]2+[\text{Fe}(\text{H}_2\text{O})_5(\text{NO})]^{2+}.
  • This is a redox reaction (pp).
  • Matching: (D)→(p)(\text{D}) \rightarrow (\text{p}).

Matching:
(A)→(p,s),  (B)→(r),  (C)→(p,q),  (D)→(p)(\text{A}) \rightarrow (\text{p}, \text{s}),\; (\text{B}) \rightarrow (\text{r}),\; (\text{C}) \rightarrow (\text{p}, \text{q}),\; (\text{D}) \rightarrow (\text{p})

Correct Answer: A

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