List of top Questions asked in CBSE CLASS XII

Out of ‘X’ and ‘Y’, which one will undergo racemisation and why?
Compound ‘X’ with molecular formula \( C_4H_9Br \) reacts with aqueous KOH to give an alcohol. The rate of this reaction depends only on the concentration of compound ‘X’. When an optically active isomer ‘Y’ of the compound ‘X’ was treated with aqueous KOH solution, the rate of reaction was found to be dependent on concentration of compound ‘Y’ and aqueous KOH both.

22(a). Write down the structural formula of both ‘X’ and ‘Y’.
Differentiate between the following :
(i) Acidic amino acids and basic amino acids
(ii) Nucleotide and Nucleoside
Why are haloarenes less reactive towards nucleophilic substitution reaction? Give two reasons.
(i) Give a chemical test to show that \( [Co(NH_3)_5SO_4]Cl \) and \( [Co(NH_3)_5Cl]SO_4 \) are ionisation isomers.
(ii) What is meant by the 'Chelate effect'? Give an example.
What type of deviation from Raoult’s law is shown by mixture of ethanol and acetone? Give reason. What will happen to the boiling point of the solution on mixing ethanol and acetone?
Assertion (A) : The two strands of DNA are complementary to each other.
Reason (R) : The hydrogen bonds are formed between specific pairs of bases.
Assertion (A) : Components of azeotropes are easily separated by fractional distillation.
Reason (R) : Components of an azeotrope have same composition in liquid and vapour phase.
Assertion (A) : Actinoids show irregularities in their electronic configurations.
Reason (R) : In actinoids 5f, 6d and 7s orbitals are of comparable energies.
Assertion (A) : The presence of \( -OH \) group in phenols directs the incoming group to ortho and para positions.
Reason (R) : \( -OH \) group in phenols activates the aromatic ring towards electrophilic substitution reaction.
Benzene diazonium chloride on reaction with phenol in weakly basic medium gives
An example of non-reducing sugar is
Which of the following is 'not' true about enantiomers?
Aniline on direct nitration yields
\( (CH_3)_3C - OC_2H_5 \) on reaction with HI gives
The secondary valency of Pt in \( [Pt(en)_2Cl_2]^{2+} \) is
How many Faradays are required to reduce 1 mol of \( Cr_2O_7^{2-} \) to \( Cr^{3+} \) in acidic medium?
Which of the following solutions will have the highest osmotic pressure?
Which of the following curve represents the first order reaction?
Which of the following is most basic?
Under which major head and sub-heads (if any) will the following items be presented in the Balance Sheet of a company as per Schedule III, Part I of the Companies Act, 2013? (i) Demand deposits with banks
(ii) Long-term loans
(iii) Livestock
Rate constant $k$ for the first order reaction is $2.54 \times 10^{-3} \text{ s}^{-1}$. Calculate the time required for three-fourth of the reactant to decompose. ($\log 4 = 0.60$)
Asha and Indra were partners in a firm sharing profits and losses in the ratio of 3 : 2. Their Balance Sheet on 31st March, 2025 was as following : Balance Sheet of Asha and Indra as at 31st March, 2025
On 1st April, 2025, Suraj was admitted for 1/4th share in the profits of the firm on the following terms : (i) Suraj will bring capital proportionate to his share in the profits of the firm. (ii) Goodwill of the firm was valued at ₹ 1,00,000 and Suraj will bring his share of goodwill premium in cash. (iii) Furniture was taken over by Asha at ₹ 1,00,000. (iv) A liability of ₹ 5,000 included in creditors was not likely to arise. (v) Plant and Machinery was revalued at ₹ 4,35,000. Prepare Revaluation Account and Partners' capital accounts on Suraj's admission. Show the calculation of proportionate capital clearly.
The concentration of the reactant is reduced from $0.6 \text{ mol L}^{-1}$ to $0.2 \text{ mol L}^{-1}$ in 5 minutes in a first order reaction. Calculate rate constant of the reaction. ($\log 3 = 0.48$)
Why transition elements form interstitial compounds?