List of top Questions asked in CBSE CLASS XII

The vapour pressure of a solvent at 283 K is 100 mm Hg. Calculate the vapour pressure of a dilute solution containing 1 mole of a strong electrolyte AB in 50 moles of the solvent at 283 K (assuming complete dissociation of solute AB).
Give the equations of reactions for the preparation of: (any three) (a) Phenol from chlorobenzene
(b) Salicyaldehyde from phenol
(c) 2-Methoxyacetophenone from anisole
Why do transition metals have high enthalpy of atomization? Which element of the 3d-series has the lowest enthalpy of atomization?
In the following pair of compounds, which compound undergoes an $\text{S}_{N}$2 reaction faster and why?
compound undergoes an SN2
Write the structures of A, B, and C in the following reactions:
structures of A, B, and C
Write the reaction involved in the following: Wolff-Kishner reduction
(b) Decarboxylation reaction
(c) Cannizzaro reaction
Write the major product in the following reaction:
ethyl chloride (CH3CH2Cl)
Define the following terms:
(a) Denaturation of protein
(b) Invert sugar
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.
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.
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.
What is lanthanoid contraction? Actinoid contraction is greater from element to element than lanthanoid contraction. Why?
Assertion (A): Uracil base is present in DNA. Reason (R): DNA undergoes self-replication.
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:
Ethanol on heating with conc. H\(_2\)SO\(_4\) at 413 K gives:
Assertion (A): Aliphatic primary amines can be prepared by Gabriel phthalimide synthesis. Reason (R): Alkyl halides undergo nucleophilic substitution with anion formed by phthalimide.
The addition of a catalyst during a chemical reaction alters which of the following quantities of the reaction?
An azeotropic solution of two liquids has a boiling point lower than either of them when it:
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:
Ligand EDTA\(^{4-}\) is an example of a:
Which of the following ligands forms a chelate complex?
Which of the following contains sp\(^2\) hybridized carbon bonded to X?
Anisole reacts with HI to give: