NEET doubts
700 doubts found
Diamond and graphite are both pure carbon — why is one the hardest natural material and the other soft enough to write with?
It's the bonding arrangement.
Why does a sealed bag of chips puff up in the sun or on a mountain flight?
Two gas laws are at work.
Why is hydrated copper sulfate bright blue, but it turns white when you heat it dry?
In the hydrated salt, water molecules act as ligands around the Cu²⁺ ion, splitting its d-orbitals so it absorbs red/orange light and reflects blue (crystal field theory).
How do I decide whether a reaction will go by SN1 or SN2?
Look at the substrate first.
Why is phenol acidic enough to react with NaOH, but ordinary ethanol is not?
Both can lose the O–H proton, but the stability of what's left decides the acidity.
How can a simple test tube reaction tell an aldehyde apart from a ketone?
Aldehydes are easily oxidised, ketones are not — and two tests exploit this.
Why does egg white turn solid and opaque when you cook it (or add acid)?
Egg white is mostly protein folded into a precise 3‑D shape held by non‑covalent interactions such as hydrogen bonds, ionic links and hydrophobic forces; the covalent disulfide (S–S) bridges are much stronger and are not broken by ordinary heating or acid.
I keep getting “The mole” questions wrong in Some Basic Concepts (Mole Concept). What's the trap?
confusing number of moles with number of grams or molecules.
I keep getting “Quantum numbers” questions wrong in Structure of Atom. What's the trap?
confusing the principal quantum number n (shell) with l (subshell).
I keep getting “Octet rule” questions wrong in Chemical Bonding & Molecular Structure. What's the trap?
forcing an octet on exceptions like BeCl₂, BF₃ or SF₆.
I keep getting “Enthalpy (H)” questions wrong in Chemical Thermodynamics. What's the trap?
getting the sign of ΔH the wrong way round.
I keep getting “Dynamic equilibrium” questions wrong in Equilibrium. What's the trap?
thinking the reaction has stopped at equilibrium.
I keep getting “Oxidation and reduction” questions wrong in Redox Reactions. What's the trap?
mixing up which process loses and which gains electrons.
I keep getting “Atomic radius trend” questions wrong in Periodic Table & Periodicity. What's the trap?
reversing the across-a-period trend.
I keep getting “Order of reaction” questions wrong in Chemical Kinetics. What's the trap?
reading the order off the balanced equation's coefficients.
I keep getting “Types of cells” questions wrong in Electrochemistry. What's the trap?
swapping which cell is spontaneous.
I keep getting “Inductive effect” questions wrong in Organic Chemistry — Basic Concepts. What's the trap?
thinking the inductive effect travels undiminished along a chain.
I keep getting “Saturation” questions wrong in Hydrocarbons. What's the trap?
thinking unsaturated hydrocarbons are less reactive than alkanes.
Why does putting salt in pasta water or antifreeze in a car radiator change the boiling/freezing point?
Both are colligative effects.
Why can metals be hammered into sheets and conduct electricity, while an ionic crystal like salt just shatters?
A metal is a lattice of positive ions in a 'sea' of delocalised electrons; when you hammer it, layers slide but the electron sea keeps holding them together, so it bends and flattens, and those mobile electrons carry current.
Why do aerosol and deodorant cans warn 'do not heat or incinerate'?
At fixed volume, a gas's pressure rises in direct proportion to its absolute temperature (Gay-Lussac's law, P ∝ T).
How do chelating agents like EDTA treat heavy-metal (lead) poisoning?
EDTA is a polydentate ligand that wraps around a metal ion at six points, forming a very stable, water-soluble chelate ring.
Why were CFCs banned for damaging the ozone layer?
Chlorofluorocarbons are so unreactive they drift up to the stratosphere intact.
Why does ethanol mix with water in all proportions, but oil-like higher alcohols don't?
Ethanol's small O–H group hydrogen-bonds strongly with water, and its tiny carbon chain barely gets in the way, so the two mix completely.