List of top Questions asked in CBSE CLASS XII

Write the major product(s) in the following reactions: 
KMnO and KOH,
What is the structural difference between nucleoside and nucleotide?
What type of linkages hold monomers of proteins together?
Give one example each for Fibrous protein and Globular protein.
What is meant by zwitter ionic form of amino acids?
What are essential amino acids?
In aqueous media, which is a stronger reducing agent — Cr³⁺ or Fe³⁺ and why?
Define lanthanoid contraction. How does it affect the atomic radii of the third transition series and the second transition series?
What is the cause of contraction in the atomic size of lanthanoids?
Why do transition metals and their compounds act as good catalysts?
How will you bring about the following conversions? (any three)
Benzoic acid to Benzaldehyde
Ethanal to Propanone
(c) Acetophenone to Benzoic acid
(d) Bromobenzene to 1-Phenylethanol
Give the structures of A, B, and C in the following reactions:
Fe/HCl.NaNO2+HCl
Give the structures of A, B, and C in the following reactions:
KCN.LiAlH4
Name the reagent used in the bromination of phenol to form 2,4,6-Tribromophenol.
Write the reactions involved in the following:
(i) Reimer-Tiemann reaction
(ii) Kolbe’s reaction
A first-order reaction is 25% complete in 40 minutes. Calculate the value of the rate constant. In what time will the reaction be 80% complete?
[Given: \( \log 2 = 0.30 \), \( \log 3 = 0.48 \), \( \log 4 = 0.60 \), \( \log 5 = 0.69 \)]
What happens when chlorobenzene and methyl chloride are treated with sodium metal in dry ether?
What type of nucleophilic substitution (\( \text{S}_\text{N}1 \) or \( \text{S}_\text{N}2 \)) occurs in the hydrolysis of 2-Bromobutane to form \( (+-) \)-Butan-2-ol? Give reason.
Why does the presence of nitro groups at ortho- and para- positions in haloarenes increase their reactivity towards nucleophilic substitution reactions?
Which halogen compound in the following pair will react faster in \( \text{S}_\text{N}2 \) reaction and why? halogen compound in the following pair
Complete and balance the following chemical equations: \( 3 \text{MnO}_4^- + 4 \text{H}^+ \longrightarrow ? \)
\( \text{Cr}_2 \text{O}_7^{2-} + 14 \text{H}^+ + 6 \text{Fe}^{2+} \longrightarrow ? \)
State a condition under which a bimolecular reaction is kinetically a first-order reaction and give an example.
In a reaction, if the concentration of reactant \( X \) is tripled, the rate of reaction becomes twenty-seven times. What is the order of the reaction?
Define molal depression constant. How is it related to enthalpy of fusion?
Write the reactions of glucose with
(a) HI
(b)\((CH_3CO_2)O\)