Match the LIST-I with LIST-II.
| LIST-I Compound | LIST-II Application |
| A. TiO | I. Oxidation of ethyne |
| B. MnO2 | II. Pigment Industry |
| C. TiCl4 and Al(CH3)3 | III. Dry battery cells |
| D. PdCl2 | IV. Polythene formation |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A-II, B-III, C-IV, D-I
Transition metals and their compounds are useful in industry in two ways. Their variable oxidation states let them act as catalysts: they form an intermediate and then change back. Some also have a useful bulk property, such as colour or being easy to reduce. Each compound in the list is a standard example.
A. TiO — This matches II. Pigment Industry. Titanium dioxide is the white pigment in paints, paper and plastics. It is valued for its brilliant whiteness, very high refractive index and chemical inertness.
B. \( \ce{MnO2} \) — This matches III. Dry battery cells. In the Leclanché dry cell, manganese dioxide is packed around the carbon rod. It oxidises the hydrogen released there and is itself reduced from Mn(IV) to Mn(III), which stops the cell from polarising:
\( \displaystyle \ce{MnO2 + NH4^{+} + e^{-} -> MnO(OH) + NH3} \)
C. \( \ce{TiCl4} \) and \( \ce{Al(CH3)3} \) — This matches IV. Polythene formation. Together these two form the Ziegler–Natta catalyst. It polymerises ethene to polythene at low pressure and gives a high-density, linear polymer:
\( \displaystyle n\,\ce{CH2=CH2} \xrightarrow{\ce{TiCl4 + Al(CH3)3}} \text{polythene, }\ce{(-CH2-CH2-)}_{n} \)
D. \( \ce{PdCl2} \) — This matches I. Oxidation of ethyne. Palladium(II) chloride is the catalyst of the Wacker process, in which ethene is oxidised to ethanal, \( \ce{CH3CHO} \). It is the only oxidation catalyst in the list.
\( \displaystyle \ce{CH2=CH2} + \frac{1}{2}\ce{O2} \xrightarrow{\ce{PdCl2/CuCl2}} \ce{CH3CHO} \)
Shortcut: The Ziegler–Natta pair C–IV is the easiest to spot, and it appears in Options (1), (2) and (4). Adding the pigment A–II leaves Options (1) and (2), and B–III then leaves only Option (2).
Note: Item I says “Oxidation of ethyne”. This wording is often quoted in textbooks, but the Wacker process actually oxidises ethene to ethanal:
\( \displaystyle \ce{CH2=CH2 + PdCl2 + H2O -> CH3CHO + Pd + 2HCl} \)
Also, item A prints TiO; the pigment is titanium dioxide, \( \ce{TiO2} \).
NCERT (2026-27 edition):
Some Applications of d- and f-Block Elements
