Identify the incorrect pair from the following:

🧠 Process-Catalyst Pairs Are Pure Recall

Industrial process questions reduce to remembering five or six classic pairings. The Wacker process is the one most students misremember as "Pt" because it sounds platinum-like. It isn't. Wacker = $\mathrm{Pd}$, specifically $\mathrm{PdCl_2/CuCl_2}$, oxidising ethylene to acetaldehyde.

🗺️ Verify Each Pair

(1) Photography – AgBr. Silver bromide is the classic light-sensitive emulsion. ✓ (2) Polythene – $\mathrm{TiCl_4}$, $\mathrm{Al(CH_3)_3}$. That's the Ziegler–Natta system for low-pressure polythene. ✓ (3) Haber – Iron. Fe with $\mathrm{K_2O}/\mathrm{Al_2O_3}$ promoters. Standard ammonia synthesis. ✓ (4) Wacker – $\mathrm{PtCl_2}$. Wrong metal: should be $\mathrm{PdCl_2}$.

Three pairs are correct, one is wrong — and the question asks for the incorrect pair.

⚡ The Periodic-Table Cousin Trap

When a process catalyst is named "Pd-something", JEE distractors almost always swap $\mathrm{Pd}$ for its row-mate $\mathrm{Pt}$. Wacker (Pd), hydrogenation (Pt or Pd) — keep the assignments straight by anchoring Wacker → Pd → "Walking the Pd dog" if you need a mnemonic.

⚠️ Common Mismatches to Beware

• Wilkinson catalyst is Rh, not $\mathrm{Ir}$ ($[(\mathrm{Ph_3P})_3\mathrm{RhCl}]$).
• Monsanto process is Rh (carbonylation of methanol).
• Ziegler–Natta is Ti + Al.
• Grubbs (olefin metathesis) is Ru.

Mixing up any of these is the standard mark-loser.

$\boxed{\text{Answer: (4) Wacker process – } \mathrm{PtCl_2}}$