Match List-I with List-II
| List-I (Compound) | List-II (Use/Application) |
| (A) Na2EDTA | (I) Hydrogenation of alkenes |
| (B) [(Ph3P)3RhCl] | (II) Estimation of hardness of water |
| (C) [Au(CN)2]– | (III) Photography |
| (D) [Ag(S2O3)2]3– | (IV) Separation of gold |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A) - (II), (B) - (I), (C) - (IV), (D) - (III)
Coordination compounds are widely used in analysis, metallurgy, catalysis and photography. In each case below, the metal ion is held in a stable complex that makes the process possible:
(A) Na2EDTA — This matches (II) Estimation of hardness of water. Hardness is caused by \( \ce{Ca^{2+}} \) and \( \ce{Mg^{2+}} \) ions. EDTA forms very stable complexes with both, so hardness is estimated by simple titration with Na2EDTA. The different stability constants of the two complexes allow each ion to be estimated separately.
\( \displaystyle \ce{Ca^2+ + EDTA^4- -> [Ca(EDTA)]^2-} \)
(B) \( \ce{[(Ph3P)3RhCl]} \) — This matches (I) Hydrogenation of alkenes. This is Wilkinson’s catalyst, a rhodium complex used as a homogeneous catalyst for adding hydrogen across a C=C bond.
\( \displaystyle \ce{RCH=CH2 + H2} \xrightarrow{\ce{[(Ph3P)3RhCl]}} \ce{RCH2-CH3} \)
(C) [Au(CN)2]– — This matches (IV) Separation of gold. In the cyanide process, gold in the ore dissolves in aqueous cyanide in the presence of air as the dicyanidoaurate(I) complex, and gold is then recovered by adding zinc.
\( \displaystyle \ce{4Au + 8CN^- + 2H2O + O2 -> 4[Au(CN)2]^- + 4OH^-} \)
\( \displaystyle \ce{2[Au(CN)2]^- + Zn -> [Zn(CN)4]^2- + 2Au} \)
(D) [Ag(S2O3)2]3– — This matches (III) Photography. After a black and white film is developed, the unexposed silver bromide is washed out with hypo (sodium thiosulphate) as this soluble complex.
\( \displaystyle \ce{AgBr + 2S2O3^2- -> [Ag(S2O3)2]^3- + Br^-} \)
Shortcut: The pair (C)–(IV) appears in Options (1) and (3), and (A)–(II) then leaves only Option (1).
NCERT (2026-27 edition):
Importance and Applications of Coordination Compounds – …
