JEE doubts
700 doubts found
What does “Filling rules” actually mean in Structure of Atom, and why does it matter for JEE?
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 JEE?
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 JEE?
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 JEE?
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 JEE?
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 JEE?
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 JEE?
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 JEE?
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 JEE?
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 JEE?
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 JEE?
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 JEE?
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 JEE?
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 JEE?
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 JEE?
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 JEE?
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.
I keep getting “Filling rules” questions wrong in Structure of Atom. What's the trap?
pairing electrons in a subshell before every orbital has one.
I keep getting “Hybridization” questions wrong in Chemical Bonding & Molecular Structure. What's the trap?
predicting geometry without counting lone pairs in the hybridization.
I keep getting “Gibbs free energy” questions wrong in Chemical Thermodynamics. What's the trap?
judging spontaneity from ΔH alone.
I keep getting “Equilibrium constant” questions wrong in Equilibrium. What's the trap?
including pure solids/liquids in the K expression.
I keep getting “Oxidising and reducing agents” questions wrong in Redox Reactions. What's the trap?
calling the substance that is oxidised the 'oxidising agent'.