List of top Questions asked in CBSE CLASS XII

(B) (a) Write chemical equations of the following reactions: (i) Phenol is treated with conc. \( HNO_3 \).
(ii) Propene is treated with \( B_2H_6 \) followed by oxidation by \( H_2O_2 / OH^- \).
(iii) Sodium t-butoxide is treated with \( CH_3Cl \).
Dr Sadao was compelled by duty as a doctor to help the enemy soldier. What made Hana, his wife, sympathetic to him in the face of open defiance from the domestic staff?
Find the local maximum value and local minimum value (whichever exists) for the function \[ f(x) = 4x^2 + \frac{1}{x}, \quad (x \neq 0). \]
Find the integrals of the function: \(sin^3 (2x+1)\)
It is natural for teenagers to have unrealistic dreams. What would you say are the benefits and disadvantages of such fantasising?

Light incident normally on a plane mirror attached to a galvanometer coil retraces backwards as shown in Fig. 9.29. A current in the coil produces a deflection of 3.5o of the mirror. What is the displacement of the reflected spot of light on a screen placed 1.5 m away?

How did the instructor “build a swimmer” out of Douglas?

Primary alkyl halide C4H9Br (a)reacted with alcoholic KOH to give compound(b).Compound(b)is reacted with HBr to give(c)which is an isomer of(a). When (a) is reacted with sodium metal it gives compound(d), C8H18 which is different from the compound formed when n-butyl bromide is reacted with sodium. Give the structural formula of(a)and write the equations for all the reactions.

Discuss briefly giving an example in each case the role of coordination compounds in:

  1. biological systems
  2. medicinal chemistry
  3. analytical chemistry
  4. extraction/ metallurgy of metals
The conductivity of 0.20 M solution of KCl at 298 K is 0.0248 Scm-1 . Calculate its molar conductivity.
Why was the Moral Rearmament Army welcomed at the Studios?

Write equations of the following reactions: 
(i)Friedel-Crafts reaction–alkylation of anisole.
(ii)Nitration of anisole.

(iii)Bromination of anisole in ethanoic acid medium.
(iv)Friedel-Craft’s acetylation of anisole.

 

The author has used gentle humour to point out human foibles. Pick out instances of this to show how this serves to make the piece interesting.
If \( x^{1/3} + y^{1/3} = 1 \), find \( \frac{dy}{dx} \) at the point \( \left( \frac{1}{8}, \frac{1}{8} \right) \).
Integrate the function: \(\frac {1}{\sqrt {8+3x-x^2}}\)
What change in the depiction of reality does the author foresee for future novelists?
Why are the young trees described as 'sprinting'?
Will Dr Sadao be arrested on the charge of harbouring an enemy?
Why are the pronouns referring to the Sun capitalised?
If a matrix has 36 elements, the number of possible orders it can have, is:
Would you agree that promises made to poor children are rarely kept? Why do you think this happens in the incidents narrated in the text?
“When a people are enslaved, as long as they hold fast to their language it is as if they had the key to their prison.”
Can you think of examples in history where a conquered people had their language taken away from them or had a language imposed on them?
(b) (ii) Which one of the following will have higher osmotic pressure in 1 M KCl or 1 M urea solution? Justify your answer.
If \( y = (\tan x)^x \), then find \( \frac{dy}{dx} \).
A function \( f \) is defined from \( R \to R \) as \( f(x) = ax + b \), such that \( f(1) = 1 \) and \( f(2) = 3 \). Find the function \( f(x) \). Hence, check whether the function \( f(x) \) is one-one and onto.