NEET · Chemistry doubts
180 doubts found
Why does a tertiary halide give a racemic (mixed left/right) product while a primary one gives a single mirror image?
A tertiary halide reacts by SN1 through a flat, planar carbocation.
Why does oxidising a primary alcohol give a different product than a secondary one?
Oxidation removes hydrogens from the C–OH carbon.
Why does a carboxylic acid have a much higher boiling point than an alcohol of similar mass?
Carboxylic acids form especially strong hydrogen bonds — in fact two molecules pair up into a cyclic 'dimer' held by two hydrogen bonds, effectively doubling the particle size.
Why does glucose give a positive Fehling's/Tollens' test but table sugar (sucrose) doesn't?
These tests need a free aldehyde (or α-hydroxy ketone) group that can be oxidised.
What does “Limiting reagent” actually mean in Some Basic Concepts (Mole Concept), and why does it matter for NEET?
the reactant that runs out first and therefore caps how much product forms.
What does “Filling rules” actually mean in Structure of Atom, and why does it matter for NEET?
Aufbau (lowest energy first), Pauli (max two electrons, opposite spins) and Hund (singly fill before pairing).
What does “Hybridization” actually mean in Chemical Bonding & Molecular Structure, and why does it matter for NEET?
atomic orbitals mix to form equivalent hybrid orbitals (sp, sp², sp³) that set the geometry.
What does “Gibbs free energy” actually mean in Chemical Thermodynamics, and why does it matter for NEET?
ΔG = ΔH − TΔS decides spontaneity — negative ΔG means the process is spontaneous.
What does “Equilibrium constant” actually mean in Equilibrium, and why does it matter for NEET?
K compares products to reactants at equilibrium; a large K means products are favoured.
What does “Oxidising and reducing agents” actually mean in Redox Reactions, and why does it matter for NEET?
the oxidising agent gets reduced (gains electrons); the reducing agent gets oxidised (loses electrons).
What does “Electronegativity” actually mean in Periodic Table & Periodicity, and why does it matter for NEET?
an atom's tendency to attract shared electrons; fluorine is the highest.
What does “Activation energy” actually mean in Chemical Kinetics, and why does it matter for NEET?
the minimum energy barrier reactants must cross; a catalyst lowers it.
What does “Electrode potential” actually mean in Electrochemistry, and why does it matter for NEET?
the tendency of an electrode to gain electrons; cell EMF = E(cathode) − E(anode).
What does “Electrophiles and nucleophiles” actually mean in Organic Chemistry — Basic Concepts, and why does it matter for NEET?
electrophiles are electron-poor (seek electrons); nucleophiles are electron-rich (donate electrons).
What does “Aromaticity” actually mean in Hydrocarbons, and why does it matter for NEET?
extra stability of planar, cyclic, fully-conjugated rings with (4n+2) pi electrons (benzene).
How does a reverse-osmosis (RO) purifier turn salty water into drinking water?
Normally osmosis drives pure water toward the salty side.
What does “Crystalline vs amorphous” actually mean in The Solid State, and why does it matter for NEET?
crystalline solids have long-range ordered arrangement and sharp melting points; amorphous solids (glass) lack order and soften over a range.
Open a perfume bottle in one corner and the whole room smells it — why, and what's fastest?
Gas molecules are in constant rapid random motion, so they diffuse and spread until evenly mixed, even against still air.
What does “Ligands & coordination number” actually mean in Coordination Compounds, and why does it matter for NEET?
ligands are electron-pair donors bonded to a central metal ion; the coordination number is how many donor atoms attach to it.
What does “Nucleophilic substitution” actually mean in Haloalkanes & Haloarenes, and why does it matter for NEET?
a nucleophile replaces the halogen; it can go by SN1 (two steps, via a carbocation) or SN2 (one step, backside attack).
What does “Acidity of alcohols vs phenols” actually mean in Alcohols, Phenols & Ethers, and why does it matter for NEET?
phenols are far more acidic than alcohols because the phenoxide ion is stabilised by resonance into the ring.
What does “Nucleophilic addition to carbonyls” actually mean in Aldehydes, Ketones & Carboxylic Acids, and why does it matter for NEET?
the polar C=O group is attacked by nucleophiles at carbon; aldehydes react faster than ketones.
What does “Basicity of amines” actually mean in Amines & Biomolecules, and why does it matter for NEET?
amines are basic because the nitrogen lone pair can accept a proton; aliphatic amines are more basic than ammonia, aniline is less.
I keep getting “Limiting reagent” questions wrong in Some Basic Concepts (Mole Concept). What's the trap?
assuming the reactant with the smaller mass is limiting.