JEE · Chemistry doubts
232 doubts found
What is the difference between ionic bond and covalent bond?
An ionic bond transfers electrons (metal + non-metal, forms ions); a covalent bond shares electrons (between non-metals).
What is the difference between system and surroundings?
The system is the reaction you study; the surroundings are everything else that can exchange heat/work with it.
What is the difference between adding heat to exothermic and adding heat to endothermic?
Heating an exothermic reaction shifts it backward (toward reactants); heating an endothermic one shifts it forward (toward products).
How do I revise Redox Reactions quickly before the exam?
One-page summary of Oxidation and reduction, Oxidation number, Oxidising and reducing agents, then timed previous-year questions.
What is the difference between group and period?
A group is a vertical column (same valence electrons, similar properties); a period is a horizontal row (same number of shells).
What is the difference between catalyst on rate and catalyst on equilibrium?
A catalyst speeds a reaction by lowering activation energy but does NOT shift the equilibrium position.
When do I use E_cell = E_cathode − E_anode in Electrochemistry, and what does it mean?
Cell EMF calculated from electrode (reduction) potentials, applicable for both standard and non‑standard conditions with proper sign conventions.
What is the difference between SN1 reaction and SN2 reaction?
SN1 goes through a carbocation in two steps (favoured by 3° substrates); SN2 is a one-step backside attack (favoured by 1° substrates).
What are the most common mistakes students make in Hydrocarbons?
Markovnikov’s rule misapplication, thinking unsaturated hydrocarbons are less reactive than alkanes, and expecting benzene to undergo addition reactions.
What does “van't Hoff factor (i)” actually mean in Solutions & Colligative Properties, and why does it matter for JEE?
the number of particles one formula unit gives in solution — about 2 for NaCl, 3 for CaCl₂, 1 for glucose.
How is The Solid State tested in JEE, and what should I focus on?
Prioritise the core ideas: Crystalline vs amorphous, Types of crystalline solids.
What is the difference between diffusion and effusion?
Diffusion is gases spreading and mixing through one another; effusion is a gas escaping through a tiny hole — both are faster for lighter molecules (Graham's law).
How is Coordination Compounds tested in JEE, and what should I focus on?
Prioritise the core ideas: Ligands & coordination number, Crystal field splitting.
How is Haloalkanes & Haloarenes tested in JEE, and what should I focus on?
Prioritise the core ideas: Nucleophilic substitution, Grignard reagent.
How is Alcohols, Phenols & Ethers tested in JEE, and what should I focus on?
Prioritise the core ideas: Acidity of alcohols vs phenols, Oxidation of alcohols.
How is Aldehydes, Ketones & Carboxylic Acids tested in JEE, and what should I focus on?
Prioritise the core ideas: Nucleophilic addition to carbonyls, Acidity of carboxylic acids.
How is Amines & Biomolecules tested in JEE, and what should I focus on?
Prioritise the core ideas: Basicity of amines, Reducing vs non-reducing sugars.
When do I use n = mass / molar mass in Some Basic Concepts (Mole Concept), and what does it mean?
number of moles from a given mass.
When do I use E_n = −13.6 Z²/n² eV in Structure of Atom, and what does it mean?
energy of an electron in a hydrogen-like atom.
What is the difference between sigma bond and pi bond?
A sigma bond forms by head-on overlap and is strong; a pi bond forms by sideways overlap of p-orbitals and is weaker.
When do I use ΔG = ΔH − TΔS in Chemical Thermodynamics, and what does it mean?
Gibbs free energy change deciding spontaneity.
When do I use pH = −log[H⁺] in Equilibrium, and what does it mean?
acidity of a solution.
How is Periodic Table & Periodicity tested in JEE, and what should I focus on?
Prioritise the core ideas: Atomic radius trend, Ionization energy, Electronegativity.
When do I use k = A·e^(−Ea/RT) in Chemical Kinetics, and what does it mean?
Arrhenius equation linking rate constant to temperature.