List of top Chemistry Questions asked in CBSE CLASS XII

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
What happens when chlorobenzene and methyl chloride are treated with sodium metal in dry ether?
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)\((CH_3CO_2)O\)
Assertion (A): Boiling point of butan-1-ol is higher than that of butan-1-amine. Reason (R): Being more polar, butan-1-ol forms stronger intermolecular hydrogen bonds as compared to butan-1-amine.
Assertion (A): Phenol on reaction with aqueous NaOH gives sodium phenoxide.
Reason (R): This reaction supports the acidic nature of phenol.
Assertion (A): \( \Delta_{\text{mix}} H \) and \( \Delta_{\text{mix}} V \) are zero for an ideal solution. Reason (R): The solution which obeys Raoult’s law over the entire range of concentration is called an ideal solution.
Which of the following Grignard reagents will be used with methanol to prepare
Grignard reagents
Which of the following elements of the 3d series of transition elements has the lowest \(\Delta_{a} H^\circ\)?

Three compounds are given below:
 
The correct decreasing order of their basic strength is:

Hoffmann Bromamide Degradation reaction is given by:
Assertion (A): Benzene diazonium salt is stable and can be easily stored.
Reason (R): Benzene diazonium chloride decomposes easily.