CUET UG Chemistry Syllabus

How does a catalyst increase reaction rate according to collision/activation theory?

A catalyst provides an alternative reaction path with lower activation energy, so a larger fraction of molecules can react; it does not change ΔH or the equilibrium position.

Give the relation for comparing rate constants at two temperatures (Arrhenius, log form).

log(k₂/k₁) = (Ea/2.303R)·[(T₂−T₁)/(T₁T₂)].

Why are transition (d-block) elements generally good catalysts?

They have variable oxidation states and partially filled d-orbitals that allow formation of intermediates/complexes and provide a surface for adsorption, lowering activation energy.

Why do transition elements show variable oxidation states?

Because the energies of (n−1)d and ns orbitals are very close, so electrons from both can participate in bonding, giving multiple oxidation states differing by one.

Explain why Zn, Cd, and Hg are not regarded as typical transition elements.

They have completely filled d-orbitals (d¹⁰) in their ground state and common oxidation states, so they lack the characteristic properties (variable oxidation state, colour, paramagnetism) of transition metals.

Why are many transition metal compounds coloured?

Due to d–d electronic transitions: an electron absorbs visible light to jump between split d-orbitals; the complementary colour is observed. Ions with d⁰ or d¹⁰ are usually colourless.

What are lanthanoid contraction and one of its consequences?

The steady decrease in atomic/ionic radii across the lanthanoids due to poor shielding by 4f electrons. Consequence: Zr and Hf (and other 4d/5d pairs) have nearly identical sizes and similar properties.

Write the formula to calculate spin-only magnetic moment of a transition metal ion.

μ = √[n(n+2)] Bohr Magnetons (BM), where n is the number of unpaired electrons.

Which transition metal ion among the first series typically shows the maximum number of oxidation states, and what is Mn's highest?

Manganese (Mn) shows the maximum range (+2 to +7). Its highest oxidation state is +7 (as in KMnO₄).

State Werner's coordination theory: primary and secondary valences.

Primary valence = oxidation state (ionizable, satisfied by negative ions); secondary valence = coordination number (non-ionizable, satisfied by ligands, directional, fixed).

Define ligand, coordination number, and denticity (with an example of a bidentate ligand).

Ligand = ion/molecule donating an electron pair to the central metal. Coordination number = number of donor atoms bonded to metal. Denticity = number of donor sites; e.g. ethylenediamine (en) and oxalate (C₂O₄²⁻) are bidentate.

What is a chelate, and why are chelate complexes more stable?

A chelate is a ring formed when a polydentate (multidentate) ligand binds a metal at two or more sites. Such complexes are extra stable due to the chelate effect (favourable entropy).

According to Crystal Field Theory, how do d-orbitals split in an octahedral field?

They split into a lower-energy triply degenerate set t₂g (dxy, dyz, dxz) and a higher-energy doubly degenerate set eg (dx²−y², dz²); the energy gap is Δo (crystal field splitting energy).

Distinguish strong-field and weak-field ligands and the resulting spin states.

Strong-field ligands (large Δo, e.g. CN⁻, CO) cause pairing → low-spin complexes. Weak-field ligands (small Δo, e.g. H₂O, F⁻) → electrons remain unpaired → high-spin complexes.

Give the order of common ligands in the spectrochemical series (weak to strong).

I⁻ < Br⁻ < Cl⁻ < F⁻ < OH⁻ < H₂O < NH₃ < en < NO₂⁻ < CN⁻ < CO (weakest to strongest field).

What type of isomerism is shown by [Co(NH₃)₅(SO₄)]Br and [Co(NH₃)₅Br]SO₄?

Ionisation isomerism — they give different ions in solution because the counter ion and a ligand are interchanged.

Name and explain linkage isomerism with an example.

Linkage isomerism arises when an ambidentate ligand can coordinate through different donor atoms, e.g. NO₂⁻ binding via N (nitro, –NO₂) or via O (nitrito, –ONO).

Why does N₂ have a much higher bond dissociation enthalpy than P₄/other group-15 elements, and how does catenation differ in group 15?

N₂ has a strong triple bond (pπ–pπ) due to small size; heavier elements form weaker single bonds and don't form pπ–pπ multiple bonds. Catenation tendency is small and decreases down the group.

Explain the trend in acidic/basic character of group-15 hydrides (NH₃ to BiH₃) and their stability.

Basic character decreases NH₃ > PH₃ > AsH₃ > SbH₃ > BiH₃; thermal stability also decreases down the group as M–H bond strength falls (NH₃ most stable, most basic).

Why is the +5 oxidation state less stable than +3 going down groups 15–16 (e.g. for Bi, Pb)?

Due to the inert pair effect — the reluctance of the ns² electrons to participate in bonding increases down the group, making lower oxidation states more stable.

Give the structure/shape of XeF₂, XeF₄, and XeF₆.

XeF₂ is linear (sp³d), XeF₄ is square planar (sp³d²), and XeF₆ is distorted octahedral (sp³d³). All have lone pairs on Xe.

Why does fluorine show only −1 oxidation state while other halogens show up to +7?

Fluorine is the most electronegative element and has no d-orbitals available, so it cannot expand its octet; hence it exhibits only the −1 oxidation state.

Why is the boiling point of HF higher than that of HCl?

Because HF molecules form strong intermolecular hydrogen bonds (F is highly electronegative and small), which require extra energy to break, raising the boiling point.

Explain why aryl halides are less reactive than alkyl halides towards nucleophilic substitution.

Due to resonance/partial double-bond character of the C–X bond, the shorter, stronger C–X bond, sp² carbon, and repulsion of the nucleophile by the electron-rich ring.

Distinguish SN1 and SN2 mechanisms (rate, stereochemistry, substrate).

SN1: two steps via carbocation, rate = k[substrate] (1st order), racemisation, favoured by 3° halides/polar protic solvents. SN2: one step, rate = k[substrate][Nu] (2nd order), inversion (Walden), favoured by 1° halides/polar aprotic solvents.

What is the order of reactivity of haloalkanes towards SN1 and the reason?

3° > 2° > 1° > methyl, because the intermediate carbocation is more stable with greater alkyl substitution (hyperconjugation + inductive effect).

Name the reaction: alkyl halide + Na metal in dry ether → higher alkane.

Wurtz reaction: 2R–X + 2Na → R–R + 2NaX (used to make symmetrical alkanes).

State Markovnikov's rule and the anti-Markovnikov (peroxide) effect.

Markovnikov: in HX addition to an unsymmetrical alkene, H adds to the carbon with more H atoms. Peroxide (Kharasch) effect: HBr adds anti-Markovnikov via a free-radical mechanism in the presence of peroxide.

Why is phenol acidic and how does it compare with ethanol and carboxylic acids?

Phenol's conjugate base (phenoxide ion) is stabilised by resonance over the ring, so phenol is acidic (pKa≈10), more acidic than alcohols/water but far less acidic than carboxylic acids.

Name the reaction converting phenol to salicylaldehyde and the one giving salicylic acid.

Reimer–Tiemann reaction (CHCl₃ + NaOH) gives salicylaldehyde; Kolbe's reaction (Kolbe–Schmitt, CO₂ + NaOH) gives salicylic acid (o-hydroxybenzoic acid).

How do you distinguish primary, secondary, and tertiary alcohols using Lucas reagent?

Lucas reagent (conc. HCl + anhydrous ZnCl₂): 3° alcohol gives immediate turbidity, 2° gives turbidity in ~5 min, 1° gives no turbidity at room temperature.

What is Williamson's ether synthesis?

Preparation of ethers by reacting an alkyl halide with sodium alkoxide (R–O⁻Na⁺ + R'–X → R–O–R' + NaX); an SN2 reaction best with primary halides.

Name the test that distinguishes aldehydes from ketones using ammoniacal silver nitrate.

Tollens' test: aldehydes reduce Tollens' reagent to give a silver mirror; ketones do not respond. (Fehling's solution gives a red Cu₂O precipitate with aliphatic aldehydes.)

What is the aldol condensation reaction?

Two molecules of an aldehyde/ketone with α-hydrogens react in the presence of dilute base to form a β-hydroxy carbonyl compound (aldol), which on heating loses water to give an α,β-unsaturated carbonyl compound.

What is the Cannizzaro reaction?

A self-redox (disproportionation) reaction of aldehydes without α-hydrogen with concentrated alkali, giving an alcohol and a carboxylate salt (e.g. 2HCHO → CH₃OH + HCOO⁻).

Why are carboxylic acids more acidic than phenols and alcohols?

Because the carboxylate ion is stabilised by resonance over two equivalent oxygen atoms (delocalised negative charge), making it more stable than phenoxide or alkoxide ions.

Arrange the basic strength of amines in the gas phase vs aqueous solution for ethyl amines.

Gas phase (only inductive): 3° > 2° > 1° > NH₃. In aqueous solution (inductive + solvation + steric): for ethyl, 2° > 1° > 3° > NH₃ (order varies due to solvation/steric effects).

Why are aromatic amines (aniline) less basic than aliphatic amines?

Because the lone pair on N is delocalised into the benzene ring by resonance, making it less available for protonation; aniline is therefore a weaker base than ammonia/aliphatic amines.

What is the carbylamine (isocyanide) test and what does it detect?

Primary amines (and ammonia derivatives) heated with chloroform and alcoholic KOH give foul-smelling isocyanides (carbylamines): R–NH₂ + CHCl₃ + 3KOH → R–NC + 3KCl + 3H₂O. It is a test for 1° amines only.

Describe the diazotisation reaction and a use of the diazonium salt.

Primary aromatic amine + NaNO₂/HCl at 0–5°C gives an arenediazonium salt (Ar–N₂⁺Cl⁻). It is used in coupling reactions to make azo dyes and in Sandmeyer reactions to introduce –Cl, –Br, –CN.

What is Hoffmann bromamide degradation and the change in carbon count?

An amide reacts with Br₂ and NaOH (aq.) to give a primary amine with one fewer carbon atom: R–CONH₂ → R–NH₂ + CO₃²⁻ (chain shortened by one C).

Classify monosaccharides and give examples of an aldose and a ketose.

Monosaccharides are classified by carbonyl group as aldoses (contain –CHO, e.g. glucose) or ketoses (contain C=O ketone, e.g. fructose), and by number of carbons (triose, pentose, hexose etc.).

Name the glycosidic linkage in sucrose, maltose, and lactose.

Sucrose: α-glucose + β-fructose via C1–C2 glycosidic linkage (non-reducing). Maltose: two α-glucose units, C1–C4. Lactose: β-galactose + glucose, C1–C4.

Distinguish starch and cellulose in terms of linkage.

Starch is a polymer of α-glucose (amylose: α-1,4; amylopectin: α-1,4 + α-1,6 branches). Cellulose is a linear polymer of β-glucose joined by β-1,4 glycosidic linkages.

What is a zwitterion and the isoelectric point of an amino acid?

A zwitterion is the dipolar form of an amino acid having both –NH₃⁺ and –COO⁻ groups. The isoelectric point is the pH at which the amino acid exists mainly as a neutral zwitterion (no net migration in an electric field).

Differentiate the primary and secondary structures of proteins.

Primary structure = the specific sequence of amino acids linked by peptide bonds. Secondary structure = local folding into α-helix or β-pleated sheet, stabilised by hydrogen bonds.

What is the difference between DNA and RNA in sugar, bases, and structure?

DNA has deoxyribose sugar, bases A,T,G,C, and is double-stranded. RNA has ribose sugar, bases A,U,G,C, and is usually single-stranded. (Thymine in DNA is replaced by Uracil in RNA.)

State the base-pairing rule in DNA (Chargaff/complementary pairing).

Adenine pairs with Thymine (A=T, two H-bonds) and Guanine pairs with Cytosine (G≡C, three H-bonds). In RNA, Adenine pairs with Uracil.

Distinguish addition and condensation polymers with one example each.

Addition polymers form by repeated addition of monomers with no loss of small molecules (e.g. polythene from ethene). Condensation polymers form with elimination of small molecules like H₂O (e.g. nylon-6,6, terylene).

Identify the monomers of nylon-6,6 and terylene (Dacron).

Nylon-6,6: adipic acid + hexamethylenediamine. Terylene/Dacron: terephthalic acid + ethylene glycol (polyester).

What is natural rubber's monomer, and what is vulcanisation?

Natural rubber is cis-1,4-polyisoprene (monomer = isoprene, 2-methyl-1,3-butadiene). Vulcanisation is heating rubber with sulphur to form cross-links, increasing strength and elasticity.

Classify polymers as elastomers, fibres, and thermoplastics with one example each.

Elastomers: weak intermolecular forces, elastic (e.g. buna-S, natural rubber). Fibres: strong forces/H-bonding (e.g. nylon, terylene). Thermoplastics: intermediate forces, soften on heating (e.g. polythene, PVC).

What is a biodegradable polymer? Give an example.

A polymer that decomposes naturally by microbial action over time. Example: PHBV (poly-β-hydroxybutyrate-co-β-hydroxyvalerate) and Nylon-2-nylon-6.

How do antacids and antihistamines work, with one example each?

Antacids neutralise excess stomach acid (e.g. ranitidine/Zantac, magnesium hydroxide). Antihistamines block H₁ receptors to relieve allergy symptoms (e.g. cetirizine, terfenadine, brompheniramine).

Distinguish antiseptics and disinfectants with examples.

Antiseptics are applied to living tissue to kill/prevent microbial growth (e.g. dettol, savlon, 0.2% phenol). Disinfectants are applied to non-living objects (e.g. 1% phenol, chlorine in water). The same substance can be either depending on concentration.

What are cationic, anionic, and non-ionic detergents? Give one example of each.

Cationic: quaternary ammonium salts (e.g. cetyltrimethylammonium bromide). Anionic: sodium alkylbenzene sulphonates / sodium lauryl sulphate. Non-ionic: esters of polyethylene glycol (no ionic charge).

Name two artificial sweeteners and an example of an antioxidant food additive.

Artificial sweeteners: aspartame, saccharin, sucralose, alitame. Antioxidant food additives: BHT (butylated hydroxytoluene) and BHA (butylated hydroxyanisole).

What are broad-spectrum and narrow-spectrum antibiotics? Give an example of each.

Broad-spectrum antibiotics kill a wide range of microbes (e.g. chloramphenicol, ampicillin, tetracycline). Narrow-spectrum antibiotics act against a few microbes (e.g. penicillin G).