List of top Questions asked in CBSE CLASS XII

An antifreeze solution is prepared by dissolving 31 g of ethylene glycol (Molar mass = 62 g $\mathrm{mol^{-1}}$) in 600 g of water. Calculate the freezing point of the solution. ($\mathrm{K_f}$ for water = 1·86 K kg $\mathrm{mol^{-1}}$)
State Kohlrausch's law of independent migration of ions. With the help of a curve, explain why it is not easy to determine $\mathrm{\Lambda^\circ_m}$ for weak electrolytes by extrapolating the concentration – molar conductivity curve, as it is for strong electrolytes.
How do you explain the following ?
(a) Presence of an aldehyde group in glucose
(b) Presence of a primary alcoholic group in glucose
Write IUPAC names of the following compounds :
(i) $\mathrm{[PtCl_2(en)_2]SO_4}$
(ii) $\mathrm{(NH_4)_2[CoF_4]}$
Define the following terms with a suitable example in each case :
(i) Ambidentate ligand
(ii) Double salt
For the compound having molecular formula $\mathrm{C_4H_9Br}$, write :
(a) the isomer which is most reactive towards $\mathrm{S_N1}$ displacement.
(b) the isomer which, on reacting with Na metal in the presence of dry ether, gives 2,5-Dimethylhexane.
For a reaction A + B → Products, the rate law is $\mathrm{Rate = k[A][B]^{3/2}}$. Write the overall order of the reaction. Can this reaction be an elementary reaction ? Give reason in support of your answer.
Assertion (A): Transition metals show their highest oxidation state with oxygen.
Reason (R): The ability of oxygen to form multiple bonds to metals.
Assertion (A): Order of reaction is applicable to elementary as well as complex reactions.
Reason (R): For a complex reaction, molecularity has no meaning.
Assertion (A): Monobromination of aniline can be conveniently done by protecting the amino group by acetylation.
Reason (R): Acetylation increases the activation effect of the amino group.
Assertion (A): Ethers have lower boiling points than the boiling points of alcohols.
Reason (R): This is due to the presence of hydrogen bonding in alcohols.
Consider the following compounds : Chlorobenzene (I), 2,4,6-trinitrochlorobenzene (II), 2,4-dinitrochlorobenzene (III), 4-nitrochlorobenzene (IV).
The correct order of increasing rate of nucleophilic substitution reactions of these compounds is :
The half-life periods of decomposition of $\mathrm{NH_3}$ for different initial pressures are given below :

The order of the reaction is :
1 mole of liquid A and 2 moles of liquid B make a solution having a total vapour pressure 40 torr. The vapour pressure of pure A and pure B are 30 torr and 45 torr respectively. The above solution :
The mole fraction of a solute in 2·0 molal aqueous solution is :
On hydrolysis, which of the following carbohydrates gives only $\mathrm{\beta}$-glucose ?
Which of the following transition metals shows +1 and +2 oxidation states ?
Which of the following product is formed when salicylic acid is treated with $\mathrm{(CH_3CO)_2O}$ in the presence of acid ?
Which reagent is used to distinguish between primary, secondary and tertiary amines ?
The correct order of decreasing basic strength in aqueous solution of the following is :
On electrolysis of very dilute aqueous solution of NaCl using platinum electrodes :
The oxidation number of Pt in $\mathrm{[Pt(en)_2Cl_2]^{2+}}$ is :
According to Werner's theory, the primary valencies of the central metal atom :
A ray of light MN is incident normally on the face corresponding with side AB of a prism with an isosceles right-angled triangular base ABC. Trace the path of the ray as it passes through the prism when the refractive index of the prism material is \( \sqrt{2} \), and \( \sqrt{3} \).
Arora and Gurmeet were partners in a firm sharing profits and losses in the ratio of 3 : 2. Starting from 1st October, 2024 Arora withdrew ₹ 30,000 at the beginning of each quarter for his personal use. Interest on drawings was to be charged @ 12% per annum. Interest on Arora's drawings for the year ended 31st March, 2025 was: