Catalytic properties — examples (V₂O₅, Fe, Ni, Pt)

3.3.6 · Chemistry › d-Block (Transition Metals) & f-Block

1. Catalysis precisely KYA hai?

2. Variable oxidation state KYU madad karta hai? (Idea ki derivation)

Maano hum chahte hain: $A + B \to A B$ , slow hai kyunki $E_{a}$ zyada hai.

Ek metal ion $M^{n +}$ jo $M^{(n + 1) +}$ ke roop mein bhi exist kar sakta hai, ek relay provide karta hai:

$M^{n +} + A \to M^{(n + 1) +} + A^{-} (metal donates? no — A oxidises metal)$ $M^{(n + 1) +} + B \to M^{n +} + B^{+}$

Ye kam energy kyun hai: har individual electron-transfer step ka $E_{a}$ chhota hota hai, jabki direct $A + B$ collision mein dono partners ko simultaneously rearrange karna padta hai (bada $E_{a}$ ). Metal regenerate ho jaata hai → catalytic.

3. Surface adsorption KYU madad karta hai? (Idea ki derivation)

Ek solid metal surface ke atoms mein unsatisfied bonding capacity hoti hai (incomplete d-orbitals bahar ki taraf point karte hain). Jab $H_{2}$ ya $N_{2}$ uske upar aata hai:

Surface d-orbitals molecule ke orbitals ke saath overlap karte hain → chemisorption (surface ke saath ek kamzor chemical bond).
Ye overlap molecule ke apne bond se electron density kheench leta hai → H–H ya N≡N bond stretchta aur kamzor hota hai.
Kamzor bonds asaani se toote/attack kiye ja sakte hain doosre reactant ke dwara → reaction low $E_{a}$ pe proceed karta hai.
Product ki affinity kamzor hoti hai → desorbs, surface ko free karta hai.

Figure — Catalytic properties — examples (V₂O₅, Fe, Ni, Pt)

4. Char exam catalysts (the 80/20 core)

5. Sirf beech ke/specific transition metals kyun?

6. Common mistakes (Steel-man + fix)

7. Active recall

Recall Quick self-test (answers cover karo)

Transition metals ke catalyse karne ke do structural reasons? → variable oxidation states + partly filled/empty d-orbitals.
Kya catalyst $K_{e q}$ badalta hai? → Nahi.
V₂O₅ oxidation-state cycle? → $V^{+ 5} \leftrightarrow V^{+ 4}$ .
Zn²⁺ kharab catalyst kyun hai? → $d^{10}$ , koi variable OS nahi, full d-orbitals.

Flashcards

Catalyst activation energy ke saath kya karta hai?

Alternative pathway provide karke

E_{a}

lower karta hai.

Kya catalyst ΔG ya K_eq badalta hai?

Nahi — sirf rate (forward aur reverse dono equally speed up hote hain).

Transition metals achhe catalysts kyun hote hain ke do reasons?

Variable oxidation states (electron relay) + partly filled/empty d-orbitals (adsorption).

SO₂ → SO₃ (Contact process) ke liye catalyst aur mechanism?

V₂O₅; homogeneous oxidation-state cycle V⁺⁵ ⇌ V⁺⁴.

Haber process ke liye catalyst aur promoter?

Fe (iron), Mo promoter ke saath; heterogeneous surface adsorption.

Vegetable oils ki hydrogenation ke liye catalyst?

Ni; apni surface pe H₂ dissociate karta hai aur C=C ke across H add karta hai.

Pt teen kaunsi reactions catalyse karta hai?

Catalytic converter (CO/NO), Ostwald process (NH₃ → NO), hydrogenation/fuel cells.

Sabatier principle kya hai?

Best catalyst reactants ko na zyada weakly na zyada strongly bind karta hai (intermediate coverage rate maximize karta hai).

Sc aur Zn kharab catalysts kyun hain?

Krama se d⁰ aur d¹⁰ hain — koi accessible variable oxidation state nahi aur koi partly filled d-orbitals nahi.

Catalyst poisoning kya hai?

Impurities (As, S, CO) ka active sites ko strongly bind karke block karna, activity khatam kar dena.

Recall Feynman: ek 12-saal ke bacche ko explain karo

Socho do shy bacche hain jo haath nahi milana chahte. Ek friendly helper (metal) pehle ek bacche ka haath pakadta hai, phir doosre ka, aur dheere se unke haath milaata hai — phir chhor deta hai, agli jodi ki madad karne ke liye taiyaar. Helper kabhi khatam nahi hota; wo sirf ek mushkil milna aasaan bana deta hai. Exactly yahi V₂O₅, iron, nickel aur platinum molecules ke liye karte hain — wo reactions jo slow hoti hain unhe fast banate hain, khud consume hue bina.

Connections

Variable oxidation states of transition metals
d-orbital electronic configuration
Activation energy and reaction kinetics
Haber process — Le Chatelier conditions
Contact process — manufacture of H2SO4
Adsorption — physisorption vs chemisorption
Catalyst poisoning and promoters