AP EAMCET / TS EAMCET Chemistry - Inorganic and Organic Chemistry Syllabus

Why does nitrogen exist as N2 (gas) while phosphorus exists as P4 (solid)?

Nitrogen forms a strong pππ triple bond (N≡N) due to its small size, giving stable diatomic gas. Phosphorus cannot form effective pππ bonds, so it forms single bonds in a tetrahedral P4 structure.

What is the trend in acidic character of Group 15 hydrides, and which is the strongest reducing agent?

Acidic character (reducing nature) increases down the group: NH3 < PH3 < AsH3 < SbH3 < BiH3. BiH3 is the strongest reducing agent. Thermal stability decreases down the group; NH3 is most stable.

Why is the boiling point of HF higher than HCl despite HCl having more electrons?

HF molecules form strong intermolecular hydrogen bonds (F is highly electronegative and small), requiring more energy to separate. HCl has only weak dipole-dipole forces.

What is the order of oxidising power of halogens and why is F2 the strongest?

Oxidising power: F2 > Cl2 > Br2 > I2. F2 is strongest due to its low bond dissociation energy, high electronegativity, and very high (negative) hydration enthalpy of F- ion.

Why are noble gases (Group 18) chemically inert and which was the first to form a compound?

They have completely filled valence shells (ns2 np6, stable octet), high ionisation energies, and zero electron affinity. Xenon was the first to form a real compound (XePtF6 by Bartlett, 1962); also XeF2, XeF4, XeF6.

What are the characteristic properties of transition (d-block) elements?

Variable oxidation states, formation of coloured ions, paramagnetism (unpaired d-electrons), catalytic activity, formation of complex ions, and formation of interstitial compounds and alloys.

Why do transition metal ions show colour?

Due to d-d transitions: an electron absorbs visible light to jump between split d-orbitals (in a ligand field), and the transmitted/complementary colour is observed. Ions with empty (d0) or fully filled (d10) configurations are colourless.

What are lanthanide contraction and one of its consequences?

The steady decrease in atomic/ionic size across the lanthanide series due to poor shielding by 4f electrons. Consequence: Zr and Hf have nearly identical sizes/properties, making them hard to separate.

Why do transition metals exhibit variable oxidation states?

Because the energies of the (n-1)d and ns orbitals are very close, so electrons from both subshells can participate in bonding, allowing several oxidation states that differ by one unit.

What is a coordination compound? Define ligand and coordination number.

A compound containing a central metal atom/ion bonded to surrounding ions or molecules (ligands) by coordinate bonds. A ligand is the electron-pair donor species; coordination number is the number of donor atoms directly bonded to the central metal.

State Werner's concept of primary and secondary valencies.

Primary valency = ionisable, satisfied by negative ions, corresponds to oxidation state. Secondary valency = non-ionisable, satisfied by ligands, corresponds to coordination number and is directionally fixed (gives geometry).

Classify ligands as monodentate, bidentate, and polydentate with one example each.

Monodentate = one donor atom (e.g. Cl-, NH3, H2O); bidentate = two donor atoms (e.g. ethylenediamine 'en', oxalate); polydentate = many donor atoms (e.g. EDTA, which is hexadentate).

What does crystal field theory explain about octahedral complexes?

It explains that ligands split the five degenerate d-orbitals into lower-energy t2g and higher-energy eg sets. The energy gap (Δo) and pairing energy determine whether the complex is high-spin or low-spin, explaining colour and magnetism.

What is the spectrochemical series and where do strong/weak field ligands lie?

An arrangement of ligands by increasing crystal field splitting: I- < Br- < Cl- < F- < OH- < H2O < NH3 < en < NO2- < CN- < CO. CN- and CO are strong field (large Δ, low spin); halides and water are weak field (small Δ, high spin).

Define the terms: mineral, ore, gangue, and flux in metallurgy.

Mineral = naturally occurring substance containing a metal. Ore = mineral from which metal is economically extracted. Gangue = unwanted impurities in the ore. Flux = substance added to remove gangue by forming a fusible slag.

What is froth flotation and which type of ore is it used for?

A concentration method for sulphide ores. The powdered ore is mixed with water, oil and a frothing agent; sulphide particles cling to the oil/froth and float, while gangue settles. Used for ores like ZnS, PbS, CuFeS2.

What is the role of carbon (coke) and the difference between roasting and calcination?

Coke acts as a reducing agent and fuel to convert metal oxide to metal. Roasting = heating ore strongly in presence of air (for sulphides, converting to oxides). Calcination = heating ore in limited/no air (for carbonates/hydroxides, removing volatile matter).

What is the basis of Ellingham diagrams in metallurgy?

They plot Gibbs free energy change (ΔG) vs temperature for formation of metal oxides. They help select a suitable reducing agent: a metal/element whose oxide line lies lower can reduce the oxide of a metal whose line lies higher at a given temperature.

What are inductive effect and its two types?

The permanent partial displacement of sigma-bond electrons along a chain due to electronegativity difference. +I effect: groups that push electrons (e.g. alkyl groups). -I effect: groups that withdraw electrons (e.g. -NO2, -COOH, halogens).

What is resonance and what is a resonance/canonical structure?

The representation of a molecule by two or more Lewis structures (canonical forms) differing only in electron arrangement. The actual molecule is a resonance hybrid, which is more stable than any single canonical form (resonance stabilisation).

Define electrophiles and nucleophiles with one example each.

Electrophile = electron-deficient, electron-pair acceptor species (e.g. H+, NO2+, BF3, carbocation). Nucleophile = electron-rich, electron-pair donor species (e.g. OH-, CN-, NH3, H2O).

What is Markovnikov's rule for addition of HX to an unsymmetrical alkene?

When HX adds to an unsymmetrical alkene, the negative part (X) attaches to the carbon bearing fewer hydrogen atoms, and H adds to the carbon with more hydrogens. This is due to formation of the more stable carbocation.

What is the peroxide (Kharasch) effect?

In the presence of peroxides, HBr adds to an unsymmetrical alkene against Markovnikov's rule (anti-Markovnikov), via a free-radical mechanism. It is observed only with HBr, not HCl or HI.

Differentiate between SN1 and SN2 mechanisms of nucleophilic substitution.

SN1: two-step, first-order kinetics (rate depends only on substrate), goes via a carbocation, favoured by tertiary halides, gives racemisation. SN2: one-step, second-order kinetics (depends on substrate and nucleophile), goes via transition state, favoured by primary halides, gives inversion of configuration (Walden inversion).

Why are aryl halides (haloarenes) less reactive than alkyl halides towards nucleophilic substitution?

Due to resonance/partial double bond character of the C-X bond (delocalisation of halogen lone pair into the ring), sp2 carbon being more electronegative, and instability of the phenyl cation. This makes the C-X bond stronger and harder to break.

What is the Wurtz reaction and the Wurtz-Fittig reaction?

Wurtz reaction: 2 R-X + 2Na -> R-R + 2NaX (forms higher symmetrical alkanes). Wurtz-Fittig reaction: an aryl halide + alkyl halide + Na -> alkyl-substituted aromatic compound (alkylarene).

How are alcohols classified as primary, secondary, and tertiary?

By the carbon bearing the -OH group: primary (1 deg) - OH on a carbon attached to one other carbon; secondary (2 deg) - OH carbon attached to two carbons; tertiary (3 deg) - OH carbon attached to three carbons.

What is the Williamson ether synthesis?

Preparation of ethers by reacting an alkyl halide with sodium alkoxide (R-O-Na): R-O-Na + R'-X -> R-O-R' + NaX. It proceeds by SN2 and works best with primary alkyl halides.

Why are phenols more acidic than alcohols?

The phenoxide ion formed after losing H+ is stabilised by resonance (delocalisation of the negative charge into the benzene ring), whereas the alkoxide ion from alcohols is not resonance-stabilised. Hence phenol releases H+ more readily.

What is the difference between aldehydes and ketones in terms of structure and one distinguishing test?

Aldehydes have the -CHO group (carbonyl with at least one H), ketones have the C=O group between two carbons (R-CO-R'). Aldehydes give positive Tollens' (silver mirror) and Fehling's tests; ketones do not.

What is the order of acidic strength among carboxylic acids and which group increases it?

Electron-withdrawing groups (-I effect, e.g. -Cl, -NO2) increase acidity by stabilising the carboxylate ion; electron-donating groups decrease it. Example: trichloroacetic acid > dichloroacetic > chloroacetic > acetic acid.