List of top Chemistry Questions asked in CBSE CLASS XII

Why do transition metals have high enthalpy of atomization? Which element of the 3d-series has the lowest enthalpy of atomization?
Write the major product in the following reaction:
ethyl chloride (CH3CH2Cl)
A 6% solution of glucose (molar mass = 180 g mol\(^{-1}\)) is isotonic with a 2.5% solution of an unknown organic substance. Calculate the molecular weight of the unknown organic substance.
Assertion (A): Uracil base is present in DNA. Reason (R): DNA undergoes self-replication.
What is lanthanoid contraction? Actinoid contraction is greater from element to element than lanthanoid contraction. Why?
A first-order reaction has a rate constant \( 1.25 \times 10^{-3} \, s^{-1} \). How long will 5 g of this reactant take to reduce to 2.5 g?
$[ log 2 = 0·301, log 3 = 0·4771, log 4 = 0·6021 ]$
Assertion (A): Diazonium salts of aromatic amines are more stable than those of aliphatic amines. Reason (R): Diazonium salts of aliphatic amines show resonance.
Assertion (A): p-Nitroaniline is a weaker base than p-toluidine. Reason (R): The electron-withdrawing effect of \(-NO_2\) group in p-nitroaniline makes it a weaker base.
The relative lowering of vapor pressure of an aqueous solution containing a non-volatile solute is 0.0225. The mole fraction of the non-volatile solute is:
During electrolysis of an aqueous solution of NaCl:
Ethanol on heating with conc. H\(_2\)SO\(_4\) at 413 K gives:
The addition of a catalyst during a chemical reaction alters which of the following quantities of the reaction?
For the elementary reaction \( P \to Q \), the rate of disappearance of ‘P’ increases by a factor of 8 upon doubling the concentration of ‘P’. The order of the reaction with respect to ‘P’ is:
Assertion (A): Aliphatic primary amines can be prepared by Gabriel phthalimide synthesis. Reason (R): Alkyl halides undergo nucleophilic substitution with anion formed by phthalimide.
An azeotropic solution of two liquids has a boiling point lower than either of them when it:
Anisole reacts with HI to give:
Which of the following is most acidic?
Which of the following contains sp\(^2\) hybridized carbon bonded to X?
Which of the following ligands forms a chelate complex?
Ligand EDTA\(^{4-}\) is an example of a:
When MnO\(_2\) is fused with KOH in air, it gives:
For an electrolyte undergoing association in a solvent, the van’t Hoff factor:
Assertion (A): Separation of Zr and Hf is difficult.
Reason (R): Zr and Hf have similar radii due to lanthanoid contraction.
Assertion (A): When NaCl is added to water, a depression in freezing point is observed.
Reason (R): NaCl undergoes dissociation in water.
Which functional groups of glucose interact to form cyclic hemiacetal leading to pyranose structure?