List of top Questions asked in CBSE CLASS XII

Who does the actual cleaning of guest rooms and bathrooms in a hotel?
The product (X) obtained in the following reaction is:
product (X) obtained
Phenol does not undergo nucleophilic substitution reaction easily due to:
Assertion (A): \( p \)-nitroaniline is a weaker base than \( p \)-toluidine.
Reason (R): The electron-donating \( -NO_2 \) group in \( p \)-nitroaniline makes it a weaker base.
Assertion (A): \( \Delta_{\text{mix}} H \) for an ideal solution is not equal to zero.
Reason (R): A–B interactions in an ideal solution are the same as between A–A and B–B interactions.
Write the chemical equations when:
(a) Ethanal is treated with 2,4-dinitrophenylhydrazine?
(b) Propanone is treated with Zn(Hg) and conc. HCl?
For a chemical reaction \( R \to P \), the variation in the concentration \([R]\) vs time \( t \) plot is given as:
variation in the concentration

(a) Predict the order of the reaction and write the unit of rate constant (\( k \)) for this order of reaction.
(b) What is the slope of the curve?
The suitable Grignard reagent used for the synthesis of
Grignard reagent

with methanal is:
All proteins on hydrolysis give:
Assertion (A): Fluoroacetic acid is a stronger acid than chloroacetic acid. Reason (R): This is due to greater electron-withdrawing nature of \( F \) than \( Cl \).
A zero-order reaction is one whose rate is independent of:
In the Arrhenius equation, when \( \log k \) is plotted against \( 1/T \), a straight line is obtained whose:
Which of the following is most reactive towards nucleophilic substitution reaction?
Which of the following has the highest boiling point?
Which of the following is the strongest acid?
Maltose is made up of:
The system that forms maximum boiling azeotrope is:
The equilibrium \( \text{Cr}_2\text{O}_7^{2-} \rightleftharpoons 2\text{CrO}_4^{2-} \):
The following initial rate data were obtained for the reaction: \[ 2\text{NO (g)} + \text{Br}_2 \text{(g)} \rightarrow 2 \text{NOBr (g)} \] initial rate data were obtained for the reaction
Write the chemical equation when:
(a) Butan-2-one is treated with Zn(Hg) and conc. HCl.
(b) Two molecules of benzaldehyde are treated with conc. NaOH.
Define colligative property. Which colligative property is preferred for the molar mass determination of macromolecules?
What happens when D-glucose is treated with the following reagents?
1 molal aqueous solution of an electrolyte \( A_2B_3 \) is 60% ionized. Calculate the boiling point of the solution.
How does the size of blood cells change when placed in an aqueous solution containing more than 0.9% (mass/volume) sodium chloride?
What is peptide linkage?